From the AP:

Jason Giambi will be sidelined at least three weeks and possibly far longer after tearing tissue in his left foot while rounding the bases on a home run. ...

While the best-case scenario likely would have Giambi returning in three to six weeks, Cashman couldn't rule out that Giambi could miss the remainder of the season.

While rounding the bases on a home run? Life happens, I guess.

Edit: Kevin Thompson has been promoted.

Via Yahoo! via KFFL.