Philadelphia’s most beloved Mummer was the best offensive lineman in the NFL in 2017, when he won a Super Bowl then rejoiced with costumed profanity.

He was the best center in 2018, though he played in perpetual pain that made him consider retiring.

Maybe he knew this was coming.

It’s easy to dump blame for the Eagles’ 5-5 ledger on their injured and inept wide receivers or their disappointing defensive backs. But no unit has played further below its expected level than the rich and healthy offensive line, and no lineman has played further below his expected level than Jason Kelce, especially in a recent, critical stretch of the season.

“I don’t agree with that. No," said offensive line coach Jeff Stoutland, gruff and defensive. "You are wrong.”

Love ya, Coach, but no, I’m not. According to Kelce.

“When there’s a play to be made, a block to be made ... I need to do it. I haven’t been doing that at the level I enjoy,” Kelce said Tuesday. “And I didn’t do it against the Patriots well enough [Sunday] to win the game.”

One of Kelce’s many virtues, and perhaps his greatest beyond public speaking, is his honesty. Another is his accountability. It’s why we love him. That, and his once-peerless play.

He posted a 61.9 grade in Sunday’s loss on the profootballfocus.com website, dropping him to 70.3 for the season. The site, its formulas, its graders, and its methods are often criticized by actual NFL evaluators, and its offensive-line ratings draw the most criticism.

But before you think PFF’s grades are unreliable or incomplete, understand that, in 2018, PFF ranked him third among all NFL linemen and first among centers, at 84.9. In 2017, Kelce led all NFL linemen with a 94.2 grade.

He was an All-Pro in 2017 and 2018, so when he was great, PFF recognized. They see a different player today. So do you.

Kelce’s 61.9 grade Sunday would have been his worst of the 15 games he finished last season, but it’s only his third-worst grade through 10 games this season. His highest grade this season was 77.8, in a loss at Detroit — a grade that would have been his fourth best in 2018 and his ninth best in 2017. He allowed 11 quarterback pressures (sacks, hits, or hurries) in 2018 and 22 in 2017. He has already allowed 18 pressures in 2019. That’s a pace for 28.

Clearly, at 32, he’s not the player he once was, but this is a remarkable drop in performance. Is it the lingering effects of the left-side litany of injuries to his knee, elbow, and foot that almost made the 2018 season his last?

No, Kelce told me Tuesday. He just isn’t playing like he used to, and bad luck seems to follow him.

For instance, against the Jets, he stumbled three times in the first half when his feet became entangled with the guards'.

“That first half was kind of a — show,” Kelce said.

Sunday evening was uglier.

Bill Belichick sent linemen and linebackers pass-rushing at all angles. Kelce is responsible for anticipating those “games” and usually is involved in squelching them. The Patriots sacked Carson Wentz five times, a season high.

The run game was productive in the first half, and it didn’t help that standout right tackle Lane Johnson exited early in the second quarter with a concussion. But, as Kelce noted, "In the second half, everybody kind of took their turn.”

Jadeveon Clowney and the Seahawks will get their turn Sunday. Clowney usually rushes from the ends, but, like most defenses, no defensive lineman stays home anymore. Kelce observed that now defenses use more twists and stunts to defeat blocking schemes without blitzing.

It also doesn’t help his grading results that, last season, PFF began to issue less stratospheric grades for linemen in general.

Packers tackle David Bakhtari led the league last season at 88.3, but that grade would have ranked just sixth in 2017 and 2016. He’d have been 13th in 2015. And while Kelce’s 84.9 grade led all centers in 2018, it would have placed him fourth in 2017 and 2015, and fifth in 2016.

His pedestrian grade this season rests largely on his combined profootballfocus.com rating for Games 5, 6 and 7. Initially, he graded at 48.7, worst among the 30 centers who played at least 75 snaps.

However, after being contacted by inquirer.com, PFF regraded Kelce. The site agreed that he’d been graded too low at 48.7 and raised his grade to 54.4. That was 25th among those 30 centers.

Kelce’s current 70.3 mark is still good for fourth among centers, and would have ranked a respectable ninth in 2018.

But Kelce needs to be much more than respectable, regardless of his grade.

“Right now, everybody needs to take accountability for the way they are playing,” Kelce said. “It’s the only way I know to get better.”