Ryan Kerrigan, the former Washington Football Team defensive end and its franchise sack leader, agreed to a one-year contract with NFC East rival Philadelphia, he and the Eagles announced Monday.

In an Instagram post Sunday night, Kerrigan thanked Washington and its fans for the past 10 years, signaling the official end of his tenure with the team and closing the door on the possibility of a return.

“I’ll never be able to sum up what these past 10 years have meant to me in an Instagram post,” he wrote, “but what I can say is that they have been some of the best of my life. I hope you had as much fun watching me as I did playing for you. Thank you, Washington, for everything.”

A former Purdue standout, Kerrigan was selected by Washington with the 16th pick of the 2011 draft and immediately became a starter — and one of the league’s most durable players. He started 139 consecutive games over his first nine seasons, earning four Pro Bowl selections in that span, before a concussion sidelined him for the first time in his career in 2019.

Last season, while playing as a reserve for the first time following Washington’s first-round selection of Chase Young, Kerrigan notched 5.5 sacks. He recorded the first two in Washington’s season-opening win against Philadelphia, which moved him past Dexter Manley (91) for the franchise record. Kerrigan, who played only 22 snaps in that game, was named the NFC defensive player of the week for his performance.

He leaves Washington with 95.5 career sacks (including 13.5 against the Eagles, tied for the most against any opponent), three interceptions (all of which he returned for touchdowns) and 26 forced fumbles, the third most of any player since 2011. He is also one of only three players, along with nine-time Pro Bowl honoree Julius Peppers and Pro Football Hall of Famer Jason Taylor, to have at least 60 career sacks and three pick-sixes.

Kerrigan became a free agent in March, but his exit from Washington appeared likely much earlier, when it was reported that he requested a trade before the November deadline last year. Kerrigan ultimately wasn’t moved, and Coach Ron Rivera stressed that he was “a big part of what we’ve done” as a player and mentor to the team’s younger players.

But in the hours after Washington’s first-round playoff loss to the Tampa Bay Buccaneers in January, Kerrigan walked back onto the sideline at FedEx Field to reminisce.

“Definitely a lot of emotions,” he said the next day. “To think I’ve been in one place for 10 years and have had the fond memories I’ve had, especially at FedEx Field, just kind of wanted to go back and relive some of those moments for a brief moment after the game. I’m glad I did that, because I’ll think on that moment and reflect on that in the years to come.”

Kerrigan said he felt he had more years left in him and wanted to be a starter. After the draft, any chance of him re-signing with Washington seemed to end when Rivera and General Manager Martin Mayhew, who selected pass rushers William Bradley-King and Shaka Toney in the seventh round, said they wanted to give their newest players a chance to prove themselves.

“We drafted these guys with the idea that these guys can contribute this year,” Mayhew said when asked about the possibility of a reunion with Kerrigan. “… We definitely plan to upgrade that position through the offseason, but we feel both of those guys have a great opportunity with us.”

Kerrigan, a surefire Ring of Famer after his retirement, stays in the NFC East with his move to the Eagles. Washington will play at Philadelphia on Dec. 18 or 19 before hosting the Eagles on Jan. 2, potentially giving Kerrigan his first opportunity to play at FedEx Field in an opposing uniform.