NEW YORK -- One of the most durable relievers of his generation and a staple of the Mets’ mid-aughts bullpens, Pedro Feliciano died on Monday. He was 45.

Feliciano had a rare genetic heart condition, which doctors first diagnosed in 2013. That became his final season in a nine-year Major League career spent exclusively with the Mets. Feliciano also played in the Dodgers, Reds and Yankees organizations, but never for their MLB teams.

“The Mets are so saddened to hear of the loss to their family today,” the club wrote in a statement. “Pedro Feliciano will be remembered as a beloved member of the Mets organization for his impact as a great teammate, as well as his reputation as one of the most competitive, durable and reliable relievers during his time in Queens. Our thoughts and prayers are with the entire Feliciano family. Rest in peace, Pedro.”

Nicknamed “Perpetual Pedro,” Feliciano was a model of durability for the talented mid-aughts Mets, appearing in 408 games from 2006-10. Feliciano led the Majors in appearances three times over that stretch, producing a 3.09 ERA over those five seasons. He appeared six more times in the 2006 playoffs, and for his career, he held left-handed hitters to a .211 average.

Feliciano’s 484 career appearances are second in Mets history behind John Franco (695). He also briefly held the franchise record for consecutive appearances (13) without allowing a hit. 

On top of that workload, Feliciano frequently made offseason appearances in the Puerto Rican Winter League, mostly for Leones de Ponce.

“I never had to call down to the ‘pen to see if he was ready,” former Mets manager Willie Randolph said. “He always was. I know sometimes he had to be tired, but he never let us know.”

Randolph added: “Forty-five is too young to die.”

ESPN’s Eduardo Pérez, who first reported the news of Feliciano’s death, wrote that the reliever passed in his sleep.

A 31st-round Draft pick of the Dodgers in 1995, Feliciano floundered in the Minors for years before first hooking on with the Mets in 2002. It would be another four years, with a stint in Japan in between, before Feliciano established himself at age 29 as one of baseball’s premier lefty specialists. Along with Billy Wagner, Duaner Sanchez and several others, Feliciano helped form the core of a 2006 bullpen that helped the staff finish sixth in the Majors in ERA.

“Just a good teammate,” was how former Mets general manager Omar Minaya recalled Feliciano. “He was a big part of that bullpen during those years. … Whatever the team wanted to do, he was always on board.

“[His career] took off late, but in those days, we valued versatility, and he was a perfect fit. It was just about giving him the opportunity.”

Following his dynamic five-season run from 2006-10, Feliciano inked a two-year deal with the Yankees, but he began experiencing arm trouble almost immediately after signing. Ultimately, Feliciano underwent rotator cuff surgery before re-signing with the Mets on a Minor League deal and attempting a comeback in 2013 -- his fourth stint overall in the organization.

That spring, doctors diagnosed Feliciano with a rare genetic heart condition. He overcame it to appear in 25 games before retiring after the season.

After news of Feliciano's death broke, various remembrances poured in from former teammates and coaches. Pitching coach Dan Warthen recalled Feliciano becoming a mentor for many young Mets, including Joe Smith -- a right-hander who pitched from a similar arm slot. Steve Trachsel called Feliciano "a machine."

"One of the great teammates I ever played with," added infielder José Valentín. "He had a great heart. He never worried about being overworked. He always put the team first."