Giambi, 36, was examined in New York on Thursday by Dr. William Hamilton, an orthopedic foot and ankle specialist. Giambi has been informed that he is suffering from plantar fasciitis and a partial tear of his plantar fascia, the band of tissue connecting his heel to his toes.
Giambi will be placed in a walking boot and is scheduled to be re-evaluated in three weeks, Yankees team spokesman Jason Zillo said. The Yankees will officially place Giambi on the 15-day disabled list prior to Friday's game at Fenway Park in Boston, where the club is set to open a three-game series with the Red Sox.
The designated hitter has been noticeably hobbled by pain in his left foot for the better part of two weeks, which has limited his ability to push off while batting because the injury affects his back, or plant, foot.
During the Yankees' recent three-game series in Toronto, Giambi had successfully lobbied the training staff to allow him to return to New York in hopes of receiving a cortisone injection in the heel of his foot, which Giambi thought would permit him to quell the pain for the series against the Red Sox.
"I do fine for one day, and then I struggle for three," Giambi said on Tuesday. "We obviously need me to be that player that I am, where I can help carry the team. Singles aren't really going to get it done. I've got to be able to drive the ball."
In 45 games for New York, Giambi is batting .262 with seven home runs and 23 RBIs. He batted just .172 (10-for-58) in his injury-marred May, though he homered in Tuesday's Yankees loss at Rogers Centre and collected three RBIs on Wednesday as the Yankees snapped a five-game losing streak.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.