The injury took place in the bottom of the fifth inning with the Reds trailing, 6-4. Hamilton reached base with a one-out infield hit and advanced to second base on a throwing error by shortstop Aledmys Diaz. Hamilton attempted to surprise the Cardinals with a quick steal of third base, but pitcher Jaime Garcia stepped off the rubber and threw to Jhonny Peralta covering to erase Hamilton from the basepaths. Peralta's tag, however, hit Hamilton in the head.
"So he has to go through the concussion protocol and clear that before we know what he's capable of doing," said Price.
Hamilton has hit .327/.353/.469 in his last 15 games and has an overall line of .269/.308/.394 this season while playing in 52 games.
Lorenzen, Iglesias improving
Right-handers Michael Lorenzen (right elbow) and Raisel Iglesias (right shoulder) completed the extended spring training portion of their rehabilitation assignments in Arizona on Wednesday and are ready for the next step in their journey back to the big leagues. For Iglesias, that means heading to Double-A Pensacola, while Lorenzen will return to Cincinnati for some side work before he goes to Triple-A Louisville for the rest of his rehab.
Price said all reports he's gotten on both pitchers have been positive.
"They both threw pain-free. The ball was coming out good, throwing strikes with a full mix of pitches," said Price.
Lorenzen has yet to pitch for the Reds this season after being injured during Spring Training. Iglesias has started five games, going 1-1 with a 3.49 ERA in 28 1/3 innings. He went on the 15-day disabled list on May 1.
Both pitchers are expected to be used out of the bullpen when they return to the Reds.
Kevin Goheen is a contributor to MLB.com based in Cincinnati. This story was not subject to the approval of Major League Baseball or its clubs.