Right-hander Daniel McCutchen has been recalled from Double-A Frisco to take Saunders' spot on the roster.
Saunders sustained the injury Friday when a line drive off the bat of Evan Longoria hit his ankle, forcing him out of the game in the fourth inning. Prior to the injury, Saunders allowed five runs (four earned) on six hits in 3 2/3 innings pitched.
"I tried to run and [the ankle] bit on me a little bit," Saunders said in the Rangers' clubhouse before Monday night's game. "It was getting better every day and then I pushed it a little bit today and it bit on me."
With Saunders' spot in the rotation vacated and an off day Thursday, starting pitcher Yu Darvish will take his turn and pitch Friday against the Houston Astros. General manager Jon Daniels said a decision has not yet been made in regard to who will replace Saunders, but he added that right-hander Colby Lewis could return to the Rangers to fill the spot.
"Reports on Colby have been pretty positive," Daniels said. "He definitely appears to be making strides and there's a good chance that we go there once we see how Colby bounces back from it."
Lewis pitched five innings for Triple-A Round Rock on Sunday, allowing four runs (two earned) on four hits and throwing 98 pitches. The 34-year-old is recovering from elbow and hip surgery that has kept him out of the majors since 2012.
Lewis can opt out of his minor-league deal with the Rangers on April 10. However, Daniels maintains that the club has an "excellent relationship" with Lewis.
"Once we make a decision we'll talk to Colby [about his option]," Daniels said. "It's something to consider but we want to most importantly bring him when he's ready to win games."
Lewis has pitched six years with Texas in his career, going 44-42 with a 4.68 ERA in 124 starts. Ron Washington, his manager from 2010-2012, said he would happily welcome Lewis back to his rotation.
"Of course, I'd like to see Colby in my rotation," Washington said.
McCutchen will be returning for his second stint with Texas this season. The 31-year-old made one appearance, allowing three runs (two earned) in 2 1/3 innings against the Tampa Bay Rays on Friday.