Manager Ron Washington said the Rangers promoted Littleton because he was next in line, ahead of such other choices as right-hander Kameron Loe.
"Littleton was the last guy we cut, and he hasn't done anything since then to tell us he wasn't ready to be here," Washington said.
In four appearances for the RedHawks, Littleton pitched six innings, allowing two runs (3.00 ERA) and a .217 opponents' batting average. He last pitched Saturday, so he was ready to pitch out of Texas' bullpen in Monday night's series opener against the Angels.
Last season, in 35 relief appearances for Texas, Littleton was 3-2 with a 4.31 ERA and two saves.
Littleton said he was "a tiny bit" surprised when he didn't make this year's team out of Spring Training.
"It was a numbers thing," he said. "I just need to be consistent. My mechanics are pretty much there, so I just needed to get some innings at Oklahoma. I was doing pretty well there."
Washington said Wright could have pitched Sunday if the Rangers' 10-inning loss to the Jays had gone much longer.
"If it went about 12, Jamey would have got one inning," Washington said. "That makes him really available tonight. We'd use him just for an inning, hopefully the seventh."
Wright's injury originally was diagnosed as a strained oblique muscle, but he said, "I've had oblique injuries twice before, and this wasn't it. We treated it with ultrasound and a lot of ice. I'm ready to go. When the phone rings, I'll do what I'm told."
Feldman, making a dual transition from reliever to starter and from a sidearm to three-quarters delivery, allowed three runs in six innings Sunday in his first big league start. He had pitched 73 times in relief for Texas between 2005-07.
Lary Bump is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.