has already etched his name in NFL lore. After just two seasons as the ' starting quarterback, Mahomes has made history by becoming the first player to win Jorge Alfaro Jersey a league and Super Bowl MVP before his 25th birthday. Earlier this week, Mahomes and his teammates received the fruit of last year's labor: a gaudy championship ring celebrating Kansas City's first title in 50 years. In 2020, Mahomes and his teammates can make more history by becoming the ninth team in NFL history to win back-to-back Super Bowls and the second team this century to accomplish that feat. The first team to win back-to-back in the 21st century was the 2003-04 , who went a combined 34-4 during that span while winning the franchise's second and third Lombardi Trophies. The 16 years since New England's 24-21 win over the in Super Bowl XXXIX represents the longest stretch between back-to-back champs. The early '70s succe sfully defended their title six years after the capped off their dynasty. The made history by winning back-to-back twice: in 1974-75 and again in 1978-79. San Francisco followed suit a decade later, winning back-to-back to cement their legacy as the Team of the '80s. The and both went back-to-back during the '90s. While a few have come close, no defending champion since the early 2000s Patriots have succe sfully defended their title, a streak the Chiefs are hoping to end in 2020. Here's a rundown of each defending champion since the '04 Patriots, along with the main reason why they were unable to repeat as champion. 2005 PatriotsRegular season record: 10-6Playoff results: 27-13 lo s to Broncos in divisional roundBiggest reason for failed repeat: TurnoversWhile their running game did them no favors (the Patriots finished 24th in rushing and 30th in yards per carry average during the regular season), New England's pa s defense, or lack thereof, was the biggest reason why the Pats lost six games during the regular season. A year after boasting one of the league's top defenses, the Patriots were 29th in the league in third-down defense, 31st in pa s defense and 27th in red-zone defense. New England certainly the lo s of Hall of Fame cornerback Ty Law, who led the NFL with 10 interceptions as a member of the in 2005.The Patriots' pa s defense, however, was not the main culprit in the team's lo s to Denver in the playoffs. Turnovers were, as five Patriot miscues including Champ Bailey's 100-yard interception return led to 17 Broncos points. 2006 SteelersRegular season record: 8-8Playoff results:NoneBiggest reason for failed repeat: InterceptionsPittsburgh lost six games by single digits. , who underwent surgery that offseason following a serious motorcycle Sergio Romo Jersey accident, threw 14 interceptions in those games. Despite throwing a league-high 23 picks (along with being sacked 46 times), Big Ben and the Steelers still managed to salvage a .500 record by defeating the in overtime in their season finale, which would serve as Bill Cowher's final game on the sidelines. The '06 season was also the last in Pittsburgh for popular pa s rusher Joey Porter, whose departure opened the door for , the franchise's all-time career sack leader.2007 Regular season record: 13-3Playoff results: 28-24 lo s to in divisional roundBiggest reason for failed repeat: TurnoversThree turnovers largely contributed to the Colts' playoff lo s to the Chargers. Leading 7-0, Marvin Harrison's fumble near the end of the first quarter set up the Chargers' first touchdown, a 14-yard touchdown pa s from Phillip Rivers to . Leading 10-7 just before halftime, 's interception to deep in Chargers territory prevented Indianapolis from extending its lead. On their first po se sion of the second half, the Colts reached the Chargers' 4-yard-line before Manning was picked off by safety . While Manning would respond with two second-half touchdown pa ses, the Colts' offensive miscues prevented them from distancing themselves from the Chargers, who received two second-half touchdown pa ses from Rivers and another score from his backup, Billy Volek. 2008 Regular season record: 12-4Playoff results: Lost 23-11 to Eagles in divisional roundBiggest reason for failed repeat: Mi sed scoring opportunitiesThe Giants' shortcomings during their playoff upset lo s at the hands of Andy Reid's Eagles included an 0-for-3 red-zone efficiency rate, two mi sed field goals, three turnovers (that included two critical fourth quarter miscues), and two unsucce sful fourth and short attempts in the fourth quarter. New York's offense also went just 3-of-13 on third down. The Giants lost despite having more than twice as many rushing yards as the Eagles. 2009 SteelersRegular season record: 9-7Playoff results: NoneBiggest reason for failed repeat: Lost fourth-quarter leadsThe '09 Steelers suffered five three-point lo ses before mi sing the playoffs for the first time under Mike Tomlin. Pittsburgh had a fourth-quarter lead in each of those games before ultimately coming up short. One blown lead that was especially painful took place at home against the in Week 13. Despite two fourth quarter scoring drives by their offense, the Steelers' defense allowed Raiders quarterback (and Pittsburgh native) to throw three touchdowns during the game's final stanza. His 11-yard touchdown pa s with le s than 10 seconds left lifted Oakland to a shocking 27-24 victory. A big reason for Pittsburgh's late-game defensive lapses was the absence of Hall of Fame safety Troy Polamalu, who mi sed 11 games due to injury.2010 Regular season record: 11-5Playoff results: Lost 41-36 to in wild card roundBiggest reason for failed repeat: Blown offensive opportunitiesAs good as the Saints' offense was in '10, they definitely left some points on the field. That fact was on display Cameron Maybin Jersey in their wild card playoff lo s to the Seahawks, a club that went just 7-9 during the regular season. The Saints' red-zone offense, ranked 20th in the NFL during the regular season, was just 4-of-7 against the Seahawks. The Saints were also on the wrong side of one of the most iconic scoring runs in NFL playoff history: 's "Beast Quake" 67-yard run that helped clinch Seattle's upset win. 2011 PackersRegular season record: 15-1Playoff results: Lost 37-20 to Giants in divisional roundBiggest reason for failed repeat: Pa s defenseLed by MVP , the '11 Packers were buoyed by an offense that averaged a league-high 35 points per game on their way to a 15-win regular season. As good as the Packers' offense was, their toothle s pa s defense was exposed by in the playoffs. Facing the league's 32nd-ranked pa s defense, Manning threw for 330 yards and three scores that included 66- and 37-yard touchdown pa ses to . The Giants went onto win the Super Bowl, while the Packers became the first team to not win a playoff game after winning 15 regular season games. 2012 GiantsRegular season record: 9-7Playoff results: noneBiggest reason for failed repeat: Lackluster run defenseWhile they finished a respectable 12th in the league in points allowed, the Giants' inconsistency against the run loomed large in their unsucce sful title defense. In six of its lo ses, New York's defense allowed 143, 191, 158, 207, 129 and 224 rushing yards. The Giants allowed two 100-yard rushers ( and ) in their Week 16 lo s to Baltimore, a lo s that ultimately sealed New York's playoff fate. 2013 Regular season record: 8-8Playoff results:NoneBiggest reason for failed repeat: Offensive woesDespite losing Hall of Famers Ed Reed and Ray Lewis, the Ravens' defense barely mi sed a beat a year after winning the franchise's second Super Bowl. Baltimore's offense, however, suffered a steep decline while playing a major role in the team's unsucce sful title defense. In '13, the Ravens' offense finished 30th in the league in rushing, 22nd in third-down efficiency and 31st in red-zone efficiency. Ray Rice averaged just 3.1 yards per carry, while threw more interceptions (22) than touchdown pa ses (19). Those turnovers were a big reason why the Ravens lost four games by three points or le s while mi sing the playoffs for the first time under coach John Harbaugh. 2014 SeahawksRegular season record: 12-4Playoff results:Lost 28-24 to Patriots in Super Bowl XLIXBiggest reason for failed repeat: A year after routing the Broncos in the Super Bowl, the Seahawks were literally on the doorstep of becoming the first team since the '04 Patriots to repeat as champion. Seattle was unable to get that last yard, however, as Malcolm Butler picked off 's pa s in the end zone to secure the Patriots' first championship in a decade. Fans still question Pete Carroll's decision to throw in that situation instead of giving the ball to Lynch, who finished the game with 133 total yards and a score on 25 touches. Carroll's defense also needs to shoulder blame, as Seattle's "Legion of Boom" secondary allowed two touchdown pa ses in the game's final eight minutes. 2015 PatriotsRegular season record: 12-4Playoff Martin Prado Jersey results: Lost 20-18 to Broncos in AFC ChampionshipBiggest reason for failed repeat: Von Miller/Peyton ManningThe Patriots' Week 12 overtime lo s to Denver prevented New England from claiming the AFC's top seed heading into the playoffs. Seven weeks later, the Patriots had to travel to Denver for the AFC title game instead of hosting the Broncos. Playing in front of a raucous Mile High Stadium crowd, the Patriots permitted a pair of early touchdown pa ses from Peyton Manning to tight end . 's interception of Brady set up Manning's second touchdown pa s. Trailing 20-12, the Patriots gave themselves a chance after Brady hit in the end zone with 17 seconds left. Brady's two-point attempt, however, was deflected and intercepted by , thus ending the Patriots' title defense. New England's rushing attack, which had been a point of concern following 's season-ending injury sustained in Week 14, was a non-factor against the Broncos, as the Patriots gained just 44 yards on 17 carries. 2016 BroncosRegular season record: 9-7Playoff results: NoneBiggest reason for failed repeat: Quarterback positionDenver's defense, led by Miller, continued to be one of the league's best a year after winning Super Bowl 50. The offense, however, fizzled out the year following Manning's retirement. That season, and completed le s than 60% of their pa ses. Without a formidable quarterback, defenses keyed in on stopping Denver's running game, which finished 27th in the league in yards gained. After a 7-3 start, Denver was unable to hide their offense down the stretch, as the Broncos lost four of their final six games to mi s the playoffs for the first time since 2010. 2017 PatriotsRegular season record: 13-3Playoff results: Lost 41-33 to Eagles in Super Bowl LIIBiggest reason for failed repeat: Malcolm ButlerThree years after being a Super Bowl hero, Butler, for undisclosed reasons, was benched for the entirety of Super Bowl LII. With Butler sidelined, Eagles quarterback relentle sly attacked New England's 30th-ranked pa s defense, throwing for 373 yards and three touchdowns. And while Brady threw for a Super Bowl record 505 yards, it wasn't enough, as Philadelphia prevailed 41-33 to win their first Lombardi Trophy. 2018 EaglesRegular season record: 9-7Playoff results: Lost 20-14 to Saints in divisional roundBiggest reason for failed repeat: Lack of receiversAfter a 5-6 start, the Eagles, led late in the year by Super Bowl MVP Nick Foles and a defense that finished first Neil Walker Jersey in the league in red-zone defense, were able to advance to the divisional round after edging the in Chicago in the wild card round. But Philadelphia's lack of playmakers ultimately caught up to them in New Orleans, where they converted on just two of their seven third-down attempts. and , the team's top two receivers, caught a combined six pa ses for 69 yards against the Saints. Trailing by six points with just under two minutes left, Jeffrey's drop led to a Saints interception that ended the Eagles' hopes of a repeat. 2019 PatriotsRegular season record: 11-5Playoff results: Lost 20-13 to in wild card roundBiggest reason for failed repeat: Lack of playmakersNew England looked downright unstoppable midway through the '19 season, winning all eight of their games by a combined score of 250-61. But as the season progre sed, the Patriots started losing their playmakers, starting with following New England's Week 2 win over Miami. The Patriots then released just before their first lo s of the season, a blowout lo s to the Ravens. Rookie receiver , the team's first-round pick, struggled with his health throughout the season. And while he caught 100 pa ses for 1,117 yards, was playing through a nagging injury heading into the playoffs. , who was acquired midway through the season in a trade with the , caught just over half of his 47 targets during the regular season. With their receiving corps depleted, Brady failed to throw a touchdown pa s in what would be his final game as a Patriot. His final pa s in New England was a pick-six that unceremoniously ended one of the greatest runs in NFL history.