The Philadelphia Eagles played their first game minus future Hall of Fame center Jason Kelce last Friday -- a 34-29 win over the Green Bay Packers in São Paulo, Brazil -- but he couldn't stay away.

When Philadelphia, clinging to a two-point lead, got down to the Packers' 1-yard line with 1:12 remaining, Kelce fired off a tweet.

"Tush push to end it!!!!!" he wrote on X.

Kelce, who now serves as an ESPN analyst on "Monday Night Countdown," got the call right. But the play didn't go as it normally does for the Eagles. The exchange between new center Cam Jurgens and quarterback Jalen Hurts wasn't clean. The ball hit the ground, and an alert Saquon Barkley hopped on the fumble to avoid a near-turnover.

Kelce's next post was Homer Simpson backpedaling into the bushes and out of sight.

The "Brotherly Shove" had only modest success in Week 1. There were four attempts total. Two failed, one was successfully converted, and the other led to an encroachment penalty on Green Bay that resulted in an Eagles first down.

So it's 50-50, which is below the lofty standards set by the team for this play. The Eagles have a success rate of 86% (61 of 71) since they started running it in 2022 -- well above the league average of 76%.

"It's unstoppable," quarterback Will Grier said. "I've watched them do it for two years now."

Well it was.

The success rate has ticked down some as of late. The Eagles got a first down on 93% of their tush push attempts in 2022 (25 of 27). In 2023, they utilized the play more and converted at a rate of 83% (35 of 42).

It appears defenses are getting better at slowing the play. And now one of the all-time greats at center is no longer in the middle of the action for Philly.

One week is a very small sample, but the results further the curiosity around one of the more discussed and debated plays in the NFL: What is the secret sauce behind the tush push? And was Kelce the main ingredient all along?

THE TUSH PUSH is a straightforward play on the surface. It's a glorified QB sneak, the only difference is there are players lined up behind the quarterback -- normally a running back and tight end -- who deliver an extra shot of momentum by pushing the quarterback forward into, and ideally through, the scrum.

The Eagles boast one of the largest offensive lines in football, with tackles Lane Johnson (6-foot-6, 325 pounds) and Jordan Mailata (6-8, 365 pounds) and left guard Landon Dickerson (6-6, 332 pounds) in the trenches. Add in a former powerlifter in Hurts, who can squat over 500 pounds, and now running back Saquon Barkley, who can lift around 600, and you have the makings for one potent short-yardage operation.

"It definitely helps how strong Jalen is and how strong I am and [tight end] Dallas [Goedert]. It's a great play," Barkley said. "That play is going to be talked about for a very long time, and it's hard to stop, so we plan on continuing to make it hard to stop."

There is more to the science equation than sheer force, however, and that's where Kelce came in.

"Kelce did such a good job of staying low consistently," Johnson said. "I think it's why we were so successful -- him and then our two guards and tackles kind of seep in and make sure there's no leakage. He did a good job with his leverage and really knowing how to execute. We're going to try and keep it to the same standard as far as execution-wise, but as you know every [Eagles] team looks different, players look different so we've still got to wait and see."

The other key element, players say, is want-to. Diving headfirst into a wall of humanity and being the low man in a pile of 300-plus-pound athletes is not for the faint of heart. The same iron man spirit that helped Kelce set the franchise record for consecutive starts (156) allowed him to serve as the lead blocker for the play time and again.

"Grit, man. Every time we did it he always said, 'Man, we've got to run it? OK.' But when he ran it, it was balls to the wall, 100%," Mailata said. "We were going to get that first down."

According to ESPN Analytics/NFL Next Gen Stats, Kelce had a 91% run block win rate on push QB sneak plays last season, 16 percentage points higher than his overall run block win rate in 2023 (75%).

The Eagles' overwhelming success executing the tush push put the play in the spotlight and fueled debate over whether it belonged in the NFL.

Former Washington Commanders defensive coordinator Jack Del Rio said he would "like to see it eliminated" before the Commanders and Eagles played last season, calling it "a nice rugby play" but "not what we're looking for in football."

The NFL competition committee was "split" over whether to outlaw the play last offseason, per Atlanta Falcons president Rich McKay, the chairman of the committee. The NFL ultimately decided in March that the play would remain legal in 2024.

"The league still likes the play, which is shocking to some people," referee Brad Allen said before the start of the season. "But the only thing [the NFL] will tell us is that on that formation, when those running backs get bunched up so close, they want to make sure there's some daylight between those running backs and the line of scrimmage. You can't put them right up in the gaps because that creates an illegal formation. That's about it. Other than that, they're good with the play, they're in a good spot with it."

Apart from size, strength and leverage, repetition has served the Eagles well. Their 71 tush push attempts since 2022 are 41 more than the next-closest team (Bills, 30).

"Obviously Kelce is a special player and Jalen is a strong guy, that certainly doesn't hurt, but compared to other teams I've been on, they just know here: it's fourth-and-1, third-and-1, they're just committing to it," Grier said.

THE LESS-THAN-stellar start on Friday should be taken with a grain of salt, Kelce believes.

"I don't know that I am the determining factor in the success of this," said Kelce on his "New Heights" podcast, noting that the play was stopped during the team's playoff loss to the Tampa Bay Bucs in January. "First of all, it's a really hard play to run when a lot of guys are running it for the first time. Once you've run it a couple times, you know how to run quarterback sneak, you get into a rhythm, and you understand how it's going to happen.

"And I think they had a new piece at center with Cam ... and then Mekhi Becton being new obviously at right guard."

Same goes for offensive coordinator Kellen Moore, "based off the circumstances of that game, I think we've got some great opportunities with the QB sneak element and keeping that as part of that package as we go.

"It's a very important play for us. ... It's a premier play, and we feel really comfortable with it.".

Jurgens, a second-round pick out of Nebraska in 2022, was a favorite of Kelce's coming out of that draft and has been coached to be his successor. Given that he was in the film room with Kelce for two years and worked alongside him last season as the starting right guard, Jurgens feels prepared.

"That's the peak of the wedge right there, so obviously make sure you've got the cadence, getting off on the snap, and that all starts with the center and the quarterback," Jurgens said.

The turf at Arena Corinthians in Sao Paulo was slick, causing issues for players on both sides. Moore said "there was an element of slipping there" on the late-game attempt at the goal line that resulted in a fumble. If the conditions were different, perhaps the success rate would have been as well.

"You can only rep that snap and the way it feels live," Kelce said. "And the reality is you are so far leaning forward trying to get leverage it's a very awkward snap to get to the quarterback if you're doing it right. I've got to think, especially with the slick field, that there were factors there that led to that fumbled one.

"I think the reality is the more reps these guys get at it, the more it's going to get back to that 90-plus percent success rate. This has done nothing to discourage me."