No one has ever played in more regular-season games for the Eagles than Brandon Graham, but there is a first for everything.

The 36-year-old defensive end this spring was an eyewitness to something he never envisioned seeing in his long and illustrious career.

He saw Saquon Barkley in Eagles’ green.

“He’s been looking good, man,’’ Graham said Monday at the St. Jude Big Daddy Celebrity Golf Classic and Gala at Cold Spring Harbor Country Club in Huntington, L.I. “It sucked that things went the way they did. Saquon is definitely in a good place right now.’’

Um, a clarification is needed here. It sucked for whom that Barkley is now with the Eagles?

“It sucked for the Giants fans because that’s like us losing our top guy,’’ Graham said, laughing. “I understand business is business, but I know Saquon definitely is looking forward to this season.’’

No doubt.

Barkley arrived to the Giants as the No. 2 overall pick in the 2018 NFL Draft.

Although turbulence with his contract caused rumblings about his time with the Giants possibly nearing an end, there remained a feeling that a parting of the ways could be avoided.

It did not happen as the Giants, after making a serious attempt to sign Barkley to a three-year deal before and after the 2022 season, declined to make a run at him after the 2023 season.

Barkley pivoted into free agency and was not on the market long before the Eagles swooped in with a three-year deal worth $37.75 million, with $26 million in guaranteed money — more than the Giants ever offered.

Just like that, Barkley switched sides in a rivalry that in his six years has been a one-sided affair.

He played in nine games against the Eagles and the Giants were 2-7 in those games.

The Giants face the Eagles on Oct. 20 at MetLife Stadium. That figures to be quite a spectacle.

“That’s gonna be like how, you know how [Terrell Owens] went to Dallas and got booed?’’ Graham said of the former Eagles wide receiver who moved on to the Cowboys. “It’s going to be one of those things. I know with [Barkley] he probably didn’t want to have to make that decision. We’re loving it because we definitely got a good player. Great dude, too. Just can’t wait to see what he does this year.’’

Giants fans who say they are fine moving on from Barkley might sing a different tune if Barkley has a big 2024 season.

“We know that people are pissed about it,’’ Graham said. “They hope that nothing comes of it. I know that’s how mad some people are about it.’’

Barkley, 27, surpassed 1,000 yards three times in his six years with the Giants and rushed for 962 yards in 14 games last season.

His time in blue was too frequently marred by injuries and shoddy offensive-line play that compromised his ability to get out of the backfield.

The Eagles, even with the retirement of center Jason Kelce, possess one of the most talented offensive lines in the league, which should be a boon for Barkley.

“I guess you’re going to have to find out,’’ Graham said. “I don’t want to predict nothing, but I know we do have a good squad and I’m expecting big things.’’

Graham, a fan favorite in Philadelphia, is returning for a 15th and final year, as he said he will retire after this season.

He has played in more regular-season games (195) than any player in franchise history.

Graham has 73 career sacks and has often been a thorn in the Giants’ side.

He earned NFC Defensive Player of the Week honors after amassing three sacks in a 48-22 thrashing of the Giants in 2022.

He will forever be a part of Eagles lore for his fourth-quarter strip sack of Tom Brady in the Eagles’ 41-33 victory over the Patriots in Super Bowl LII.

Going against Barkley, Graham recalled there were rules the Eagles tried to follow.

“You just can’t let him hit the hole, that’s the biggest thing,’’ Graham said. “Once he hits the hole, he’s a home run hitter. I know for Saquon, he always was the guy you don’t want to see with daylight.’’

Now he and Barkley are teammates and Graham can hardly believe it.

“That’s one thing that just don’t happen,’’ he said. “That’s just like me playing all these years and then going to play with the Cowboys. Or the Giants, the rival. It’s just the way business was handled, I felt, that’s probably why he wanted to come over here. I know he’s been as advertised.’’