Baker responded by saving the bullpen, pitching 5 1/3 innings of relief after starter Colby Lewis allowed seven runs in 3 2/3 innings.
"We're just trying to get the bullpen straightened out so we're going to have to go a player short for the next couple of days," manager Ron Washington said.
Baker is an eight-year Major League veteran who spent 2005-11 as a member of the Twins rotation. He underwent Tommy John surgery in April of 2012 and did not return to the Major Leagues until late last season when he pitched in three games for the Cubs.
The Rangers signed him to a Minor League contract in Spring Training and he was 4-1 with a 3.32 ERA in six starts for Round Rock.
"It was obviously a long road," Baker said. "But I was really enjoying myself down there, it was a great group of guys. But everybody is striving to be here and it really makes it special when you endure something like this. Physically I feel as good as I ever have."
Baker, who is from Shreveport, could have become a free agent on May 1 since he was not added to the 25-man roster by that day. He said he elected to stay with the Rangers because it was close to home and he had made significant progress working with Triple-A pitching coach Brad Holman.
"It made no sense, even if there wasn't a Major League opportunity, to go anywhere else," Baker said. "This was the ideal situation."
Baker has made 162 Major League starts and four relief appearances with a record of 63-48 with a 4.14 ERA. He won a career-high 15 games with the Twins in 2009. But he will be used in relief with the Rangers.
Washington said there are no plans for Baker to replace Robbie Ross in the rotation. Ross is 0-3 with an 8.10 ERA in his last four starts.
"We haven't discussed moving anybody," Washington said.
T.R. Sullivan is a reporter for MLB.com Read his blog, Postcards from Elysian Fields and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.