PHILADELPHIA (973espn.com) — Jason Kelce is supposed to be one of the Eagles' best players but when watching the film, it's clear that the Pro Bowl center has taken a major step back in the 2015 season.

His performance against Ndamukong Suh and Miami was one of his worst of the campaign, resulting in three holding penalties and another poor shotgun snap. According to the playing-rating website Pro Football Focus, it was Kelce's sixth negative grade of the season against just three positive games.

After the loss, a frustrated Kelce called it the worst game of his professional career. With a few days to mull that analysis over that veteran tempered his self-scouting a bit on Tuesday.

“Physically, I don’t think I played that bad during the game," Kelce claimed. "There were a couple play Suh got me, but other than that, I felt I handled a lot of situations really well.”

So why the harsh assessment on Sunday?

“I think I was really hard on myself because it’s just been a really frustrating season for me,” he said. “I’ve had a lot of penalties, a lot of really dumb mistakes, mental mistakes, poor fundamentals. It’s been things that have just kind of culminated over the season."

That's certainly the hope of Chip Kelly and the Eagles because mental mistakes and poor fundamentals can be cleaned up. A physical decline is far tougher to deal with.

“I just think he's hot and cold,” Kelly said when asked about Kelce. “I think against Dallas Cowboys, Jason played an outstanding football game. Carolina Panthers -- I thought he played a really good game. And (the Miami game) game, he didn't play the way Jason expects himself to play, and we understand that."

Understanding it and correcting it are two different things, however, and it's getting tougher to picture the light going on for Kelce this season.

Apologists have pointed to the fact that the veteran center is playing next to a pair of lesser-regarded guards, first the now-injured Andrew Gardener and Allen Barbre, and now Matt Tobin and Gardner.

The party line is that Kelce has been trying to overcompensate for the deficiencies surrounding him but early in the season Gardner was playing better than Kelce and at times in recent weeks Barbre has been better.

“I wouldn’t say that’s the issue,” offensive coordinator Pat Shurmur said when asked about the guard play. “Sometimes, you just have a handful of bad plays. ...It’s a unit and they play as a unit.”

What is known is the Eagles best games up front have been the three that Kelce has excelled in so maybe it's time for the former sixth-round pick to scale things back and handle his own assignment before trying to help others.

"Sometimes I’m trying to do too much," Kelce admitted. "...Instead of trying to do more, (I need to) just go back to the fundamentals. Make sure you block the guy (in front of me).”

-John McMullen covers the Eagles and the NFL for 973ESPN.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen