The Rangers have 10 days to trade, release or outright Padilla to the minors.
Padilla, the Rangers' No. 2 starter when the year began, is 8-6 with a 4.92 ERA this season, his fourth with Texas. He lost to Oakland in his last start on Wednesday, his second outing after a bout of swine flu.
Padilla won 43 games in four years with Texas, but already has been put on waivers this season. He angered the organization earlier this year by throwing at hitters, including two incidents involving former teammate Mark Teixeira.
Texas also recalled outfielder Julio Borbon from Triple-A Oklahoma City.