That rotation is subject to change as the Trade Deadline approaches. Gallardo, Lewis and Rodriguez are all free agents after the season, the Rangers still have Nick Martinez and Chi Chi Gonzalez at Triple-A and Anthony Ranaudo in the bullpen, and they have Derek Holland getting closer to returning off the disabled list.
The next two weeks will determine the direction of the rotation although the Rangers are still hoping their starters can carry them back into the division race.
"Our starting rotation has the opportunity to take us to where we need to go," Rangers manager Jeff Banister said Thursday. "But we need to continue to play strong defense and we need our veteran hitters to swing the bats well for us."
The Rangers could still move Rodriguez, even if they stay in the race. It would allow them to bring Martinez or Gonzalez back to the big leagues. Clubs have told the Rangers that Rodriguez could be a fallback option if they are unable to land a more significant starting pitcher in a trade.
Gallardo, who was 7-8 with a 2.62 ERA in 19 starts, could bring the biggest return of any of the Rangers' starters. But the Rangers will likely wait until right up to the Trade Deadline before they decide if they will make him available. The Rangers won't want to move him if they feel they are still in the race.
The Rangers are still unsure of what they will get from Harrison. He underwent spinal fusion surgery on June 3, 2014, and made his first start since then on July 8, allowing six runs in four innings against the D-backs. His velocity was also down significantly.
The Rangers expect Perez to make a smoother transition off the disabled list. He had a 4.56 ERA in six rehab starts in the Minors, but the reports suggest his velocity and his stuff are back to pre-injury quality.
"I feel I am at that level," Perez said. "I feel strong. I can throw the ball where I want it and I have my velocity. If you can put the ball where you want it with velocity, it's a big deal. Now I just have to throw strikes."
Holland, who has been sidelined for over three months with a strained muscle in his left shoulder, is scheduled to throw in the bullpen on Saturday. If that goes well, he could move up to live batting practice while the Rangers are in Colorado.
T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, follow him on Twitter @Sullivan_Ranger and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.