A bit more than a year removed from his last major league appearance, Billy Wagner took the mound at Citi Field last night in the top of the eighth inning against the Braves. His entrance was greeted with loud cheers, and those cheers grew as he struck out the first man he faced and then completed his one-two-three inning with a second whiff. Wagner left the mound to the better part of a standing ovation, the crowd sounding a bit like it was celebrating the tension of a critical late-season game.

That’s not where the Mets were, though. The team Billy Wagner left last August 2 was two games out of first place in the NL East. The team he returned to is playing out the string in a lost year. The raucous cheers for Wagner, understandable for a good and popular player returning from a serious injury, fell flat to me. It was the absence of Wagner down the stretch in the last two seasons that was the single biggest reason the Mets missed the playoffs in those years, the single biggest reason for the enormous amount of pressure on the 2009 team. Wagner was intermittently available in ’07, watching his teammates blow leads in at least one critical game that September and himself losing two, including one to the Phillies in late August. By suffering a season-ending injury in early August last year, Wagner forced the Mets to use lesser relievers at a point in the season where finding substitutes would be difficult. Wagner’s hero’s welcome was dissonant.

The 2009 Mets are done, of course, and the absence of Wagner is one reason for that. The Mets invested in Francisco Rodriguez and J.J. Putz this winter, and might have used resources in other ways had they had a healthy Wagner. Had payroll been allocated differently, the team might have been better prepared for the brutal wave of injuries that ended its season gradually. For it is injuries, now to all four of the team’s best position players, that are the defining story of the 2009 Mets.

Carlos Delgado played his last game on May 10. Through that day, the Mets were 17-13, having scored 151 runs in 30 games, or a tick more than five per game. May 10 was the last time the Mets were whole. Jose Reyes made his last start of the season May 20, and played just about 10 innings between May 13 and his last appearance, just one full game. Mark May 13 and see that the Mets were 18-15 and had scored exactly five runs per game; that was when Reyes hit the DL.

Playing without two of their top players, the Mets struggled to score runs. Over the next five weeks, through June 21, the team went 16-18 and scored 145 runs, 4.3 per game. That’s when Carlos Beltran‘s bum knee pushed him out of the lineup. Without Reyes, Delgado and Beltran, the Mets fell apart: 21-29, 3.8 runs per game. Finally, last Saturday, David Wright was beaned, and he hasn’t played since. The Mets are 1-3 without him and have scored just 3.5 runs per game in that span.

Each injury made the team a little bit worse until there was nothing left. It’s rare you find a pattern this clear in any data, but with the 2009 Mets, the situation is crystal-clear: they got a little bit worse with each lost starter until they simply couldn’t field a decent lineup. With none of the players having returned, they never reassembled the offense that was supposed to push them into contention. Injuries, so often an excuse, are clearly the sole cause of the Mets’ disappointing 2009.

There’s a guiding principle in baseball that you don’t lose your job because of injury. To fire Omar Minaya would be to fire him because half his payroll got hurt. If you want to criticize him for not having better depth, that’s your prerogative, but this Mets bench wasn’t bad. Alex Cora, Gary Sheffield, Fernando Tatis, Angel Pagan… that’s a good bench. The problem is that it’s been the starting lineup on far too many nights. The Mets had Cory Sullivan batting fifth last night. They play Jeff Francoeur-and it’s not the wrong move. They gave Angel Berroa a look. No GM can be expected to succeed if all of his best players get hurt, and that’s what happened to the Mets this year. Minaya, who assembled an improved bench and bullpen this year, isn’t the reason this team isn’t in contention.

The Mets could have used a healthy and effective Billy Wagner down the stretch in 2007, and even a cutdown version of the left-hander would have been useful a year ago. Now, he’s ready to pitch, but the roles have been reversed, and it’s his teammates who watch helplessly from the sidelines as a season fades away. Wagner’s best way of contributing to the Mets now is to pitch well between now and next weekend, which may allow the team to trade him and get some return for a player who’s contract expires-well, there’s an option year, but good luck getting that picked up-in six weeks. It would be funny if Wagner has a greater impact on the Mets’ fortunes in 2011 and 2012 via the return he brings the club in a trade than he had in the last three years in which he was wearing blue and orange.