From young phenom to ripened reliever, Jason Isringhausen has come full circle with the New York Mets.

Hoping to help their beleaguered bullpen, the Mets brought back a prodigal son Monday when Isringhausen joined the team for the opener of a four-game series against the Colorado Rockies.

Once a prized starter and part of a much-hyped trio nicknamed Generation K, the 38-year-old Isringhausen is back with the Mets for the first time since 1999.

"It feels good so far," Isringhausen said before the game. "I'll give 'em everything I've got."

Derailed by a string of elbow injuries, the two-time All-Star had not pitched in a big league game since June 13, 2009, with Tampa Bay. But first-year Mets manager Terry Collins was planning to use Isringhausen as soon as possible.

"I'd like to get him in the fire," Collins said.

He did just that. Isringhausen entered with two runners on in the seventh and retired both batters he faced, getting pinch-hitter Todd Helton on a soft fly to center to end the inning.

After keeping the score tied at 4, Isringhausen pumped his fist as he walked off the mound. He flashed a smile and was greeted warmly by teammates in the dugout.

"Yeah, my heart was pumping a little bit. I was nervous, but that's what makes it fun," Isringhausen said after New York's 7-6 loss.

The Mets also called up right-hander Ryota Igarashi from Triple-A Buffalo, putting eight relievers in a taxed bullpen that had a 4.98 ERA after nine games.

To make room on the roster, they optioned outfielder Lucas Duda to Buffalo and designated right-hander Blaine Boyer for assignment after Sunday's 11-inning loss to Washington.

New York relievers threw 11 innings during a three-game series last weekend, allowing 10 hits and 11 walks. That's one reason Collins was willing to play with just a four-man bench, at least for a little while.

"We've got to protect our starting pitching," he said. "I'm more concerned with blowing our bullpen out before June."

Isringhausen, who has 293 career saves, had been throwing at extended spring training in Florida. Attempting his latest comeback, he signed a minor league deal with the Mets on Feb. 15 after a brief bullpen audition.

The right-hander has had Tommy John surgery on his pitching elbow three times during his 14-year career, but he was effective in Grapefruit League action this spring, going 1-0 with a 1.13 ERA in eight outings covering eight innings.

After pitching in seven games for Cincinnati's Triple-A affiliate last year, he was looking for an opportunity this season when the Mets agreed to give him a shot.

"When my agent told me this, I said, 'Yeah, this will be fun,'" said Isringhausen, who is wearing No. 45. "My wife and I talked about it. Full circle, and everything happens for a reason. So I'm going to run with it as much as I can. I don't know what's going to happen — nobody does. So when they call on me, go out there and give it everything I've got and let the chips fall where they may."

Isringhausen was selected by the Mets in the 44th round of the 1991 free agent draft and they converted him from a college outfielder to a pitcher. He made his major league debut in 1995, going 9-2 with a 2.81 ERA in 14 starts and finishing fourth in NL Rookie of the Year voting.

Along with No. 1 draft pick Paul Wilson and left-hander Bill Pulsipher, Isringhausen was part of a young pitching threesome that was supposed to lead the Mets to years of success.

"The talk on the bench was, 'Oh my god, when these guys grow up, holy cripes, this staff is going to be something special,'" said Collins, who was managing the Houston Astros at that time. "They all certainly had very, very, very good arms."

But all three got injured and Isringhausen was traded in July 1999 to Oakland, where he became a quality closer. He signed with St. Louis in December 2001 and had five seasons with more than 30 saves for the Cardinals, including a league-high 47 in 2004.

Isringhausen said it hurt to be traded by his original big league club, but he quickly moved on.

"Been a lot of games between then and now," he said. "It was hard, but I wouldn't change the path of my career for anything. ... It's been a long road."

Isringhausen said he doesn't have many specific memories from his first stint with the Mets, other than striking out Brian McRae of the Chicago Cubs to begin his major league debut.

"I'm not near that person I was then. To me, I feel like I'm a better person," Isringhausen said. "I was real immature, and pretty much an idiot back then."

But now, his intangibles are a big reason he's back, and Collins made it clear that he wants his young relievers to soak up some of Izzy's veteran expertise.

First, Isringhausen had to find his way around Citi Field. When he pitched for the Mets the first time, they played at Shea Stadium.

"It's still the Mets on the chest. That never changes," he said. "This could be it, so I'm going to give it 110 percent every time I get the ball."