The Cardinals placed Rajcic on the 15-day injured list Monday with a right elbow injury.
Manager Oliver Marmol revealed that Rajcic felt elbow soreness after his last appearance Friday, and he's being sent for a second opinion before a more specific diagnosis is revealed, per Jeff Jones of the Belleville News-Democrat. The rookie reliever has yielded five runs with an 8:6 K:BB over nine innings out of the Cardinals' bullpen since being called up last month.