The injury has not affected the performance of Salas, who owns a 2.96 ERA and has surrendered only one run in his past five appearances. He tossed two scoreless innings and earned the victory in the Angels' 11-6 win against the Braves on Saturday.
"I think he's making his pitches," Scioscia said. "But it's becoming tough for him to rebound and get loose and things that are eventually going to affect his velocity and command, and that's important to him."
De La Rosa owns a 4.24 ERA in 85 career Major League innings and has compiled a 3.73 ERA in nearly 500 innings during 11 seasons in the Minors.
Joe Morgan is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.