OAKLAND, CALIF. ? The Oakland Athletics traded their second top starter in three days, sending left-hander Mark Mulder to the National League champion St. Louis Cardinals on Saturday for a package of prospects.

Mulder follows Tim Hudson out of town, leaving Barry Zito as the only remaining member of Oakland’s vaunted “Big Three” pitchers. Hudson was dealt to Atlanta on Thursday for three mostly unproven players.

Mulder could be the top-notch pitcher the Cardinals sorely lacked when they were swept by the Boston Red Sox in the World Series, but that’s if he’s healthy. In return, the A’s acquired pitchers Danny Haren and Kiko Calero and minor-league catcher Daric Barton.

Mulder’s finish last season was perplexing.

The 6-foot-6 lefty, the AL starter in the All-Star game, seemed destined for Cy Young award consideration midway through the season, but went winless in his last seven starts — 0-4 with a 7.27 earned-run average.

On Aug. 24, he became the first 17-game winner in the majors, then didn’t win again. There was speculation he was hurt and not telling anyone.

Mulder (17-8) pitched so poorly during the playoff push, the A’s briefly considered skipping his turn and using September callup Joe Blanton during the final weekend against Anaheim. Mulder did get the call, but was knocked out after two innings, his shortest outing of the season — and the A’s wound up missing the playoffs for the first time in five years.