In the 1990 Tom Hanks film “Joe Versus the Volcano” (a classic to some, though not many), Dan Hedaya has a long, one-sided phone conversation that mostly consists of him repeating the phrase, “I know he can get the job, but can he do the job?” That question may well apply to the Mets, who are in a good position to make it to the postseason, but may not have what it takes to win in the postseason.

The formula for October success is slightly different from that of the regular season, as teams such as the Braves and the A’s have discovered to their detriment, despite winning division title after division title. As Baseball Prospectus has documented in its book “Baseball Between the Numbers,” the attributes that most closely correlate with winning in the fall are having a strikeout-oriented pitching staff, a tight defense, and a top closer. The reason for this is rather obvious when you stop to think about it: The teams that make it to the postseason are the good ones, and when the good teams put the ball in play, things happen.

Consider a bad team, such as the Mariners. In any game, they might have as many as two legitimate home-run threats in the lineup. They might have as many as four hitters whose overall production could be considered average. Even if they put runners on first and second to start an inning, the opposition has a good chance to escape without giving up more than one run, because assuming that the third batter of the inning makes contact — if that hitter is Yuniesky Betancourt or Jeremy Reed or Kenji Johjima — the result might be a single or a groundout, not a three-run homer.

Now consider the Mets in the same situation. In most games, they will have at least six batters in the lineup who can do some real damage if they come up to bat with runners on. If Jose Reyes puts bat to ball, he might hit a triple; David Wright might hit a double, or Carlos Delgado a home run (as he did in yesterday’s game against the Brewers), and so on down the order until you run into a second baseman or a catcher. This is true of all teams at all times, but it is especially true when facing a good one — the only way to be completely safe is to keep the ball from leaving the catcher’s mitt.

The Mets are well-situated in two of these three areas, with a defense that has been among the league’s most reliable at turning balls in play into outs, and a pitching staff that, primarily due to the efforts of Johan Santana and Oliver Perez, is a tick above average in its strikeout rate. It is the third area, closing, that — with Billy Wagner currently out and perhaps even when (or if) he’s back in — encompasses the whole shaky bullpen apparatus, owning the potential to undermine the Mets’ chances of playing beyond the first round if they succeed in winning the National League East.

No one who has watched Mets’ relievers struggle to finish games this year would doubt the importance of the bullpen to this particular team, but the bullpen problems will only be heightened in the postseason. The reasons for this are, again, not particularly hard to puzzle out. When good teams meet, in all probability with their best pitchers lined up against each other, the games are far less likely to be one-sided. Close games require solid work from the bullpen, work the Mets largely haven’t gotten. That is why, at least in part, Jerry Manuel allowed Nelson Figueroa to try to protect a 4-2, eighth-inning lead against the Brewers yesterday, in a game that both had implications for the division title andwas a possible playoff preview. The choice of Figueroa was no doubt initially dictated by the fatigued state of the pen after the Mets required five relievers to finish out Pedro Martinez’s start on Sunday, but his remaining in the game also represented an attempt by Manuel to catch relief lightning in a bottle. In this case, it didn’t work — Figueroa allowed a leadoff double to Ryan Braun, and Manuel was forced to go to usual standbys Pedro Feliciano and Joe Smith. In a display of excellence that’s unusual for the Mets this year, they combined to whiff the next three batters, Prince Fielder, Corey Hart, and Mike Cameron. This was a shocker — to date, the Mets have been one of the worst teams in the majors at stranding runners on base. Only five clubs — among them the Padres, Orioles, and Nationals — have been worse.

Ironically, of late the Mets have been turning to Luis Ayala, a pitcher out of that hapless Nats’ bullpen, to close out their games in Wagner’s absence. As a reliever, Ayala is notable for his low strikeout rate, a fact thatbrings us full circle to the importance of keeping the ball in the catcher’s mitt. Ayala got the save yesterday. But it’s not just finishing the games — it’show you finish them that matters in October.

Mr. Goldman writes the Pinstriped Bible for yesnetwork.com and is the author of “Forging Genius,” a biography of Casey Stengel.