Once they do, Andy Parrino will be promoted, MLB.com has learned. The versatile infielder/outfielder, brought over in the offseason in the trade that sent Tyson Ross to the Padres, enjoyed a nice spring with the A's and was batting .174 (4-for-23) in six games with the River Cats through Tuesday.
Parrino hit .207 with one homer and six RBIs in 55 games with San Diego last year, appearing in 26 games at shortstop and 15 at second base, while also playing two games at third and one in right field.
Sizemore sustained the injury in the fourth inning of Tuesday's contest while chasing after a fly ball off the bat of Mike Trout that fell in for a hit. He exited the game and was replaced by Eric Sogard.
"I just kind of stopped, kind of with a straight leg, and it didn't feel right," Sizemore said. "It kind of tightened up on me. ... We'll get it checked out tomorrow and hopefully it's something minor and won't be anything too serious. But, as of now, we don't know anything."
Sizemore underwent surgery on that same knee just last spring as a result of a torn ACL, forcing him to miss all of 2012. Tuesday marked just his second appearance of the season.
Best-case scenario, Sizemore learns that the pain is stemming from scar-tissue tearing.
"That would be good," he said, "but at this point, it's just kind of all speculation, so we just wish for the best."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.