Sizemore was scheduled to undergo an MRI exam to determine the extent of the injury. The Athletics open the season on March 28 against Seattle in Tokyo, and it was uncertain whether Sizemore would be ready by then.
A Comcast Sports Net Bay Area cameraman captured the aftermath on film, which shows Sizemore with his arms around two of the team's personnel, with A's manager Bob Melvin also at the scene. He was not putting any weight on his left foot.
"You don't like to see that happen on the first day," Melvin said. "On top of that he's an integral part of the team. You feel bad for him."
Sizemore, who came to the A's in a trade with the Detroit Tigers last May, batted .249 with 11 home runs and 52 RBIs in 93 games with Oakland.
Sizemore was expected to be in the opening day lineup at third base. Melvin said the team will look to a combination of Eric Sogard, Adam Rosales, Josh Donaldson and Wes Timmons as a replacement.
Donaldson, who appeared in the major leagues with the A's briefly in 2010, took over for Sizemore and later went behind the plate to catch live batting practice. Originally a first-round draft pick of the Chicago Cubs, Donaldson was traded to the A's in a deal that sent Rich Harden to the Cubs.
Manny Ramirez faced major league pitching for the first since last April, stepping in against Jerrod Parker and Tyson Ross for a combined 15 pitches. He swung at four pitches, making contact on three of them, one a line drive. Ramirez later told a Japanese reporter that he would not be going to Japan for the exhibition games before the A's-Mariners two-game series to start the 2012 major league season. ... The A's coaching staff will be watching Sunday's Academy Award ceremonies with a special interest. General manager Billy Beane, the focus of the movie, "Moneyball," will be at ceremony. The movie received six Oscar nominations.