The Angels placed ace Jered Weaver on the 15-day disabled list on Tuesday because of a non-displaced radial head fracture in his left elbow, an injury that will sideline the right-hander for at least four weeks.
Initial X-rays of the elbow taken Sunday night in Texas were negative, and Weaver, who jammed the elbow as he hit the ground to avoid a vicious Mitch Moreland line drive up the middle, was diagnosed with a strain.
But further tests in Southern California on Monday revealed a more significant injury, and the Angels will be without their best pitcher, a 20-game winner in 2012, for at least a month and possibly more.
The Angels are expected to replace Weaver in the rotation with right-hander Garrett Richards, a starter-turned-reliever who has allowed one earned run and three hits in 4-1/3 innings of four appearances this season.
To replace Weaver on the roster, the Angels called up right-hander Dane De La Rosa, a reliever who was acquired from Tampa Bay for pitcher Steven Geltz on March 27. De La Rosa, a native of Torrance, has a 10.95 ERA in 12 big-league games, allowing 15 earned runs in 12 1/3 innings for the Rays.