Romo missed 12 games in 2015 after he broke his left collarbone twice. He begins this year on the sideline after suffering a back injury in the preseason.

The four-time Pro Bowl quarterback is clearly on the decline.

Here are other players who could trend downward in 2016:

Jason Peters, LT, Eagles: He's an eight-time Pro Bowl pick and two-time All-Pro who has missed only two games in the past three seasons. But the 34-year-old Peters isn't the dominant blocker he used to be. He has 18 penalties and 12 sacks allowed over the last two seasons.

Chris Johnson, RB, Cardinals: Johnson was on his way to his seventh 1,000-yard season in eight years before getting hurt last season. He ran for 814 yards in 11 games. His injury gave David Johnson an opportunity to play more and he was dynamic. The Cardinals are in good hands with either Johnson, but expect David to get the ball more than Chris.

Demaryius Thomas, WR, Broncos: Thomas had 105 catches for 1,304 yards and six TDs in 2015 despite Peyton Manning's rapid decline. But the Broncos are a far more run-oriented offense under Gary Kubiak, who can emphasize his system in Year 2 now that Manning is gone and Trevor Siemian is the quarterback. Thomas will get the ball, but he's not going to catch triple-digit passes in this offense.

Mario Williams, DE, Dolphins: After racking up 38 sacks between 2012-14, Williams had just five sacks in 909 snaps last season. He was released by the Bills following a disappointing year playing linebacker in Rex Ryan's 3-4 system. Miami is banking on Williams being more comfortable in the 4-3, but Williams' best days could be in the past.

Arian Foster, RB, Dolphins: Foster missed 23 games for the Texans over the past three seasons due to back, groin and Achilles tendon injuries. He's a 30-year-old running back who took a lot of hits and has suffered a lot of injuries. That adds up to less production.