Giambi tried to play himself back into shape following treatment for a benign tumor, but he went 4-for-33 (.121) after he was activated from the disabled list on Sept. 14. He hit a career-low .208 this season with 12 homers and 40 RBI.
Yankees manager Joe Torre said last month that it would be a "longshot" that Giambi would be left off, but in the weeks since, the need to carry an extra pitcher grew because Hernandez developed a tired shoulder and Vazquez continued to struggle.
With John Olerud playing well at first base, Giambi at best would have been used as a designated hitter or pinch-hitter against the Twins.
"He's had a tough year, both physically and emotionally,"
Torre said last month. "Spring training on through, he's had a tough time.
It's not easy all of sudden, here I am playing baseball when it
looked for so long like it wasn't going to happen."