Watt may not be NFL's clear-cut best defender upon return from back injury

J.J. Watt has already cultivated a resume that would place him among the best defenders in NFL history at the age of 28, which he turns Wednesday.

Watt and Lawrence Taylor are the only players to win Defensive Player of the Year three times, and the Houston Texans' superstar wreaked havoc upon taking his first professional snap. Amassing 76 sacks over the course of six seasons, Watt is on a trajectory that few players have encountered in NFL history.

However, there's reason to be concerned about Watt moving forward after his 2016 season was truncated due to a back injury, limiting him to three games. Watt advertised himself throughout his career as the picture of resilience, but severe back injuries seldom go away, even with a lengthy rehab stint. Although Watt's teammates - namely Jadeveon Clowney and Whitney Mercilus - stepped up in his absence, Watt enters the latter stages of his prime bearing a tremendous workload, one that may predispose him to further damage. Prior to the 2016 season, Watt never missed a game in his career, but it'll be an uphill battle to reclaim his throne.

Meanwhile, a host of young, captivating defenders have made a stake for Watt's claim as the top defender in football, with Khalil Mack, Von Miller, and Aaron Donald all making cases to supersede him.

Mack's body of work over the past two seasons presents a particularly strong argument to be considered as the NFL's preeminent defender. The 26-year-old became the first player to be named a first-team All-Pro at two different positions in 2015, which could be viewed as an indictment of the voter base, but speaks to his resolute versatility. Mack followed up his 2015 campaign by seizing Defensive Player of the Year honors, commandeering the Oakland Raiders to their first playoff appearance since 2002, a stint that likely would've been elongated had Derek Carr not suffered a season-ending leg injury in Week 16. Sharing the same pedigree as Watt as an overlooked collegiate recruit who rose to prominence, Mack is two years younger and is rapidly improving, while Watt spent a year brooding on the sidelines.

Pro Football Focus named Donald as its Defensive Player of the Year for the second consecutive year, shedding the institutional bias against interior linemen. Donald is a bona fide superstar and while he isn't lauded by casual fans as often as his edge rusher counterparts, there's a genuine argument to be made that he's the best defensive player irrespective of position. PFF presented Watt with the award from 2012-2014, but there may be a permanent shift as a younger, healthier cohort emerges at the forefront.

Miller almost won his first Defensive Player of the Year award last season, losing to Mack by one vote. If Miller walked away with the trophy, it would've cemented his career mantle, already owning multiple first-team All-Pro selections, along with a Super Bowl MVP award. Miller is Watt's contemporary, selected in the exemplary 2011 NFL Draft, and has racked up four more forced fumbles (19 to 15) in five more games (88 to 83). A narrative built around "rings" would grow tiresome, but Miller, who celebrates his 28th birthday on Sunday remains in peak form and injury-free, leading arguably the NFL's best defense.

None of the above cases are meant to dismiss what Watt has achieved. He would be inducted into Canton without much thought if he opted to retire tomorrow, an untenable option for someone who's branded himself as the ultimate competitor. There may not be a deeper pool of defensive talent than there is now, and Watt will reenter the league with a tenuous hold on the title of the NFL's best defensive player.