NEW YORK -- Widely considered one of the three most accomplished pitchers in Mets history, Jerry Koosman will soon have a permanent place at Citi Field to recognize his achievements.

On the 50th anniversary of clinching their first National League East title, the Mets announced Tuesday that they will retire Koosman’s No. 36 during a ceremony next summer. Koosman will join Tom Seaver (No. 41) and Mike Piazza (No. 31) as the only Mets players to have their numbers retired.

“He was honored to be the next guy,” Mets chief operating officer Jeff Wilpon said. “Obviously, he knows the two other men that are up there. Following in their footsteps and being recognized for what he did in ’69, 50 years later, is pretty neat. I think it bookends our celebration of the ’69 season pretty well.”

• Mets' all-time retired numbers

Earlier this summer, the Mets brought most living members of the 1969 Mets to Citi Field to celebrate the 50th anniversary of their World Series title. Few played a more significant role in winning it than Koosman, who finished 17-9 with a 2.28 ERA in 241 innings. The staff’s clear No. 2 starter behind Seaver, Koosman threw a total of 17 2/3 innings over two World Series victories, including a complete game in the deciding Game 5.

Koosman ranks second in team history behind Seaver in starts (346), complete games (108), innings (2,544 2/3) and shutouts (26); third behind Seaver and Dwight Gooden in strikeouts (1,799); and sixth in ERA (3.09).

“The excitement of playing for the Mets when we won the 1969 World Series was an experience I never thought I’d be able to repeat,” Koosman said in a statement. “But the news that the Mets Hall of Fame Committee has voted to retire my number is another life-changing thrill and honor.”

Four years after Koosman’s retirement, in 1989, the Mets inducted him into their franchise Hall of Fame. But the team, which ranks among baseball’s strictest in terms of retiring numbers, refrained from retiring his No. 36 for another three decades. In addition to joining Seaver and Piazza, Koosman will join managers Gil Hodges (No. 14) and Casey Stengel (No. 37) on the left-field roof at Citi Field, as well as Jackie Robinson, whose No. 42 is retired throughout baseball. The Mets also recognize broadcaster Ralph Kiner and executive Bill Shea with signs in that area.

Koosman will become the first player not in Cooperstown that the Mets will honor in this way, hinting at a loosening of the franchise’s standards. Wilpon has hinted that the Mets plan to retire David Wright's No. 5 in the coming years, despite the fact that Wright is unlikely to enter the National Baseball Hall of Fame. The Mets also have no representatives from the 1986 team in their retired numbers area; Gooden, Keith Hernandez, Gary Carter, Darryl Strawberry are all possibilities to change that, even though none of the latter three spent more than eight years in Flushing. All four are already in the Mets Hall of Fame.

“I think we see the fans want it,” Wilpon said of the potential relaxing of retired number standards. “Now that we’re 50 years plus in the making, there’s time to do it. Some guys have cemented themselves. There’s a plan going forward for Hall of Fame and number retirement. We’re going to spread them out, not to overload anything. But I think we have a plan to catch up and do some neat things for the fans.”

That will begin next summer with the retirement of Koosman’s No. 36. Until Tuesday, current Mets manager Mickey Callaway wore No. 36, which he traded in for No. 26 out of respect to Koosman. Callaway said he spoke to several members of the 1969 Mets during the team’s anniversary celebration in June, and he was blown away by the compliments they offered once they saw his No. 36 threads.

“They said the most unbelievable things about [Koosman],” Callaway said. “I’m so proud to have worn this jersey for almost two years as a Met. That’s pretty cool that it’s going to be up on the side of the stadium, where it belongs.”