Considering all things, it’s pretty astonishing that the Mets are only three games out of the wild-card lead. The last week saw Carlos Beltran, Mike Piazza, and Mike Cameron miss time with brutal injuries while the team somehow managed to blow a game in which Pedro Martinez allowed only two hits and nearly blew another in which he left after six innings up 8-0.

That the Mets have won more than they’ve lost since the awful Cameron-Beltran collision is due largely to some excellent starts from the likes of Jae Seo and Kris Benson, the freakishly great hitting of David Wright, and some luck. But for that luck to keep up, the Mets are going to have to make some changes. The playoffs are very much within reach, but if a tight, five-way race leaves little margin for error, the injuries to Cameron and Piazza have left the Mets with none.

The basic problem is self-evident: The Mets have some serious holes, some of which can’t be fixed this late in the season. There isn’t much to do about the lack of production from the rotating cast of backup second basemen who are manning the right side of the infield. With Cameron out for the rest of the year, the defensive foibles of Victor Diaz will simply have to be tolerated in the hopes that his bat will make up for his roundabout routes to fly balls and his habit of letting line drives roll around in the outfield so that Beltran can throw the ball in to the infield. That leaves the bullpen, which may be the team’s biggest weakness right now; happily, it’s also the one most easily taken care of.

As will be evident to anyone who saw Saturday’s game against the Nationals, the first move has to be to follow up on yesterday’s overdue demotion of Dae-Sung Koo with a similar demotion for Danny Graves, who along with Koo coughed up six runs in one inning to turn a 8-0 laugher into a near-disaster.

Don’t count me among those inanely criticizing manager Willie Randolph for turning to these two in that game. Taking Martinez out after the sixth inning with an 8-run lead was a wise move-the Mets’ ace will need to be strong down the stretch for the team to win, and it’s a good idea to get him some rest when possible. Neither was using Graves and Koo a poor idea; if you can’t trust a man with an 8-run lead in the seventh, there’s no point in having him on the roster. As it turns out, there’s no point in having either on the roster, something the Mets have accepted in Koo’s case and now need to accept in the case of Graves. In Saturday’s game he walked the first batter he faced. With an 8-run lead, that’s just unacceptable.

The second move is just as obvious. Braden Looper shouldn’t pitch to another left-handed hitter in a save situation for the rest of this season, insofar as that’s possible. Lefties are pounding him this year, hitting .312 BA/.385 OBA/.548 SLG – essentially, he’s turning every lefty he faces into Cubs third baseman Aramis Ramirez, who ranks in the top 10 in the league in average, home runs, RBI, and slugging percentage. That’s not good.

The first step toward a solution should be to announce today that both lefty Royce Ring and righty Heath Bell have been called up. Neither pitched particularly well in their stints in Flushing earlier this year, but both have good minor league track records and showed real signs of putting it all together when they were in the majors. I could reel off some statistics here, but the reasoning is far more basic – they couldn’t possibly be any worse than Graves, and if they managed to give up six runs in one inning, it could at least be viewed as on-the-job training, an investment in the team’s future. When veterans like Graves-who have no future with the team – do so, it’s an investment in nothing.

As to Looper’s problems with southpaws, the answer is sitting right there in the Mets’ bullpen. Aaron Heilman, with his funky delivery and nasty changeup, is just the sort of pitcher you’d expect to be more effective against lefties than righties, and this year he has indeed exhibited something of a reverse platoon split – lefties are hitting .226/.307/.301 against him, while righties are hitting .269/.309/.347. There’s no earthly reason why he shouldn’t be brought in instead of Looper with the game on the line and, say, Philadelphia’s Bob Abreu and Chase Utley due up in the ninth.

There are good and valid reasons for settling on one pitcher like Looper as a designated closer, but the pennant race is too tight not to go with the best pitcher in every situation, reputations be damned. Randolph has shown signs of recognizing this – the ill-fated experiment with using Koo against lefties in the ninth proves that. Now it’s time for him to go all the way with the idea.

There are other things the Mets can do with the bullpen to improve their chances. Designating Steve Trachsel as a long relief specialist and milking some longer appearances out of the durable Heilman and Looper should be on the agenda. But the really crucial thing is to avoid putting the ball in the hands of anyone who doesn’t give the team a chance to win. That sounds obvious, but once you’ve seen Dae-Sung Koo brought in to help protect a slim lead, you know it needs to be said again and again.