Rooker was pulled from Thursday's game against the Yankees in the first inning due to right flank discomfort, Martin Gallegos of MLB.com reports.
Rooker tweaked his side on a swing and was removed from the contest mid at-bat. He will undergo imaging Friday, Gallegos adds, before more is known about Rooker's condition, but a trip to the injured list could be in the cards. If Rooker is forced to miss time, it could result in additional playing time for Carlos Cortes and/or Andy Ibanez.