TORONTO – Jason Giambi’s struggles might have cost him a spot on the Yankees’ postseason roster.

Before the Yankees ended the regular season yesterday with a 3-2 win over Toronto, Yankees manager Joe Torre outlined some of his decisions heading into the first round series against Minnesota.

Mike Mussina (12-9) will pitch the opener tomorrow night against Johan Santana (20-6), and Jon Lieber (14-8) will pitch the following night against Brad Radke (11-8).

Torre hinted he might keep 11 pitchers on his roster against the Twins, including Kevin Brown and Orlando Hernandez, both candidates to start Game 3 next Saturday at the Metrodome. El Duque has been bothered by a tired arm in his last two starts.

Torre liked what he saw from Brown on Saturday, and it sounds as if Brown will get a start if Hernandez doesn’t. “I’m glad that Kevin has jumped into the fray. There’s no question that we’ll consider him,” Torre said.

That decision could mean Giambi won’t be included. He was 0-for-4 with two strikeouts yesterday – fanning with the bases loaded and two outs in the first. Giambi dropped to 4-for-33 (.121) since he was activated from the disabled list.

“He looked like he was more frustrated today than any other day,” Torre said. “It’s just not happening for him.”

Torre said he’ll announce a decision after today’s workout. He’s thought about using Giambi as a pinch hitter.

The Yankees, who clinched the AL East on Thursday, finished the regular season 101-61, joining Atlanta (1997-99), Baltimore (1969-71), and the Philadelphia Athletics (1929-31) as the only teams with three straight 100-win seasons.

With the Yankees having clinched their seventh straight division title, Torre again selected a veteran player to manage the final game of the regular season, picking Ruben Sierra. In 1996, Sierra called Torre “a liar” when they clashed over Sierra’s playing time, but Sierra has gotten along well with teammates and management during his second stint with the Yankees, which began last year.

Sierra jokingly imitated Torre’s walk when making a pitching change in the eighth inning.

“He milked it. I thought he went overboard,” Torre joked.

Scott Proctor (2-1) pitched the seventh inning for the win in relief of Brad Halsey, who allowed one run and five hits in five innings. Bernie Williams put the Yankees ahead with his 22nd homer, a drive in the eighth inning.