As the saying goes, Father Time is undefeated. It’s a cold reality that is about to set in for a handful of NFL stars who are in danger of seeing their production fall off the proverbial cliff. Here’s a look at five AFC players who could be in for a letdown in 2015. We’ll examine NFC players next week.

QB Peyton Manning (Broncos) 

Some positions age better than others, with pocket quarterbacks ranking at the top of that list. But anyone who watched Manning over the second half of last season knows his regression was about more than a thigh injury. His already limited arm strength dropped below functional levels, which is even more of an issue for a team that plays its December and January homes game in a winter wonderland.

Manning, 39, will now attempt to fend off Father Time under the direction of a new coaching staff. And he’ll have to get it done playing behind an offensive line that lost Ryan Clady (injury) and Orlando Franklin (free agency) from last season’s group.  He’s also missing one of his top touchdown-makers after Julius Thomas jumped ship to the Jaguars. Add it all up and it’s easy to see how a fall-off is inevitable.

New coach Gary Kubiak has even taken to lightening Manning’s offseason workload to try to save him for later in the season.

“It’s not like we’re in there resting by any means. We’re doing more intense lifting than the guys that are doing the team work,” Manning said. “I still feel like we’re practicing, we’re just doing some alternate things.”

RB Frank Gore (Colts)

While quarterbacks typically age well, running backs fall off the cliff faster than any other position. That doesn’t bode well for Gore, 32, who is already coming off a down season in which he averaged his fewest yards per game since becoming a starter back in 2006.

Gore is a power runner who has absorbed a lot of hits over the years because of his refusal to avoid contract. That served him well in San Francisco, where he faced more eight-man fronts than any other runner in the league last season, but it makes him less likely to sustain his success in Indianapolis.

Gore, of course, does not want to hear that all those hits are going to take a toll.

“I live by this, I will never let a man tell me what I can’t do because I turned a certain age,” he said earlier this offseason. “As long as I got passion and love for the game, I’m going to try and be the Frank Gore I’ve always been and that’s what I go by.”

DE Chris Clemons (Jaguars) 

As we covered in a recent piece about player-coach connections, Clemons signed his deal with the Jaguars last offseason because of his relationship with Gus Bradley as much as anything else. That helps explain why the Jaguars gave a four-year contract to a player who will be 36 years old by the time it expires.

Clemons, 33, enjoyed a nice first season in Jacksonville. He led the team with eight sacks and also chipped in four forced fumbles and three passes batted down. However, edge rushers are prone to sudden fall-offs because they rely so much on speed and explosiveness.

The plan was for No. 3 overall pick Dante Fowler to take over as the Jaguars’ primary pass rusher this season. Unfortunately, Fowler tore his ACL during rookie camp, meaning Jacksonville needs to squeeze at least one more season of QB pressures out of Clemons. It’s a risky proposition, especially for a defense that will spend a quarter of its season chasing around Andrew Luck and Marcus Mariota.

TE Antonio Gates (Chargers)

The plan was to scale back Gates’ workload last season. Backup TE Ladarius Green was one of the breakout stars of 2013 and the plan was for Green and Gates to be evenly involved in 2014. It didn’t work out that way, though, as Green’s progress plateaued and Gates delivered a renaissance season (69 catches for 821 yards and 12 touchdowns).

Gates, 35, thoroughly enjoyed turning back the clock, but that didn’t stop him from coming out earlier this offseason and openly asking for a lighter workload.

“With injuries and whatnot, I played a little bit more than they expected me to play last season,” Gates said, via Emily Kaplan of MMQB.com. “I was playing the whole game. How I feel next year, it depends on how much volume they have me doing. I’d like to come in on third-and-7s, red zones, those situations. That’s what my contribution is at anyway.”

That’s fine with the Chargers, who are determined to see that they have in Green as the fourth-year tight end is entering the final year of his contract.

Offensive coordinator Frank Reich said recently he’d be “shocked” if 2014 is not Green’s biggest season. By extension, we should all be “shocked” if Gates’ numbers don’t take a corresponding dive.

OT Andrew Whitworth (Cincinnati) 

Whitworth was ranked as the third-best offensive tackle in the league last season, according to Pro Football Focus, not allowing a single sack and giving up just nine quarterback pressures. So why the belief that the 33-year-old blindside protector is primed for some serious slippage? That’s a question for the Bengals, who hedged their bets by spending their first two draft picks on offensive tackles Cedric Ogbuehi and Jake Fisher.

Whitworth, predictably, believes his best work is still ahead of him.

“Honestly, I feel even better this year,” he said. “I was still in that window (last year) from a knee injury. In the (last) offseason I trained really hard but didn’t think I could fully do everything I do now. I worked out hard, but I didn’t run that much. This year I have done it all.”

Cincinnati’s coaches have done nothing but praise Whitworth, but actions speak louder than words. By spending a pair of premium picks on offensive tackles, Cincinnati has all but assured Whitworth will not be back after his contract expires in March. You don’t go down that road with an elite player unless he is rapidly approaching the drop-off zone.

Which other players are in danger of falling off the cliff? Talk about it with author Michael Lombardo during his weekly NFL Chat on Friday at 2pm EST. But you don’t have to wait until then … you can ask your question now!