If you were starting a team from scratch and could pick one young National League starter, San Diego’s Jake Peavy would be right there with Florida’s Dontrelle Willis, Houston’s Roy Oswalt, and Chicago’s Carlos Zambrano and Mark Prior among those you’d have to seriously consider.

There’s nothing imposing or physically impressive about the Padres’ 24-year-old ace; generously listed at 6 feet, 182 pounds, he has a lot more in common with Oswalt than with Roger Clemens. He compliments a fine fastball with a nasty slider and change-up, but there are probably two dozen starters his age with stuff as good. All Peavy has done is lead the league in strikeouts (this year) and earned run average (last year),while showing a fine grasp of the principle behind the success of the Atlanta Braves pitching staffs of the last 15 years, which is that the best pitch you can throw is one low and away with some movement on it.

You have to admire his guts, too. After he gave up eight runs in 4 1 /3 innings to the Cardinals in the first game of their NL Division Series yesterday, putting his team in a 1-0 hole from which it has next to no chance of recovering, it came out that Peavy had aggravated a rib injury in the third inning – a malady through which he tried to pitch. (Peavy said he might have bruised his ribs during a celebratory scrum after the Padres clinched the NL West on Wednesday. He said the injury was probably worsened when he caught his spike on the rubber on a wild pitch in the third yesterday).The nature of pitching mechanics being what they are, Peavy was probably endangering his career in trying soldier on; overcompensate for an injury by changing your arm slot a bit, and there goes your shoulder. This sort of thing happens all the time.

Assuming nothing worse goes on, all that happened to Peavy was that he gave up eight runs, which is one more than he’d given up in any game this year. It’s a shame for him and for the Padres that their season may end because of a freak injury, and a good break for the Cardinals, but it also goes a long way to show why the playoffs are not exactly the contest of skill and baseball virtue they are often made out to be.

Going into this series, a quite plausible case could have been made that the Padres were equal to the Cardinals. Their roundly mocked 82-80 record indeed painted them as a weak team, but it also didn’t necessarily have a lot of relevance to their playoff chances. Second baseman Mark Loretta and catcher Ramon Hernandez, each among the best in the league at a key position, played in only 206 games between them this season, but got healthy in time for the playoffs. Sean Burroughs, one of the great wastes of talent in the last 20 years, cost the team wins earlier this year with his inept slap-hitting; third-sacker Joe Randa, a midseason acquisition, is no Mike Schmidt, but he is a lot better than Burroughs. The Padres team playing in October is stronger than the one that ran up a mediocre record, and due to various injuries and slumps, this Cardinals squad is weaker than the team that won 100 games.

None of that matters now. The Padres’ chances were predicated on a healthy, rested Peavy winning two games in the five-game set, or at least winning one and forcing the Redbirds to beat two other San Diego pitchers and the strikeout champion – by no means impossible, but not easy, either. Now the Cardinals have not only beaten Peavy, but they won’t have to face him again, as the broken ribs, confirmed by an MRI after the game, will force him out for the rest of the series. Barring divine intervention, the Cardinals are going to their fourth National League Championship Series in six years.

By this time next year – by this time next week, even – the role of Peavy’s injury will be all but forgotten, even by many San Diego fans. In retrospect, the victory of the 100-win Cardinals over what is still, despite any compliments, the weakest team in the playoffs will seem to have been inevitable, and evidence that in the playoffs, the best teams advance toward the end of crowning the best the World Champion.

A broken rib for an enemy pitcher doesn’t say a lot about how good Jim Edmonds, Albert Pujols, and Chris Carpenter are, though, and it’s on just such flukes that pennants are so often built. Think only of Mariano Rivera – how, after blowing series against the Diamondbacks and Red Sox, is he still regarded as utterly invincible? Because everyone who saw him falter in those crucial moments saw that the hitters were hitting pool-cue shots off him that had barely any right escaping the infield, let alone plating winning runs.

Such is baseball, though. The Cardinals will win this series, and may finally win it all this year, but right from the get-go it will have as much to do with luck and fortune as anything else.

tmarchman@nysun.com