"Obviously we are cutting deep into our depth," manager Jeff Banister said. "It's not perfect. We're at the stage of the year in baseball where things can happen. You build yourself for these types of situations. These times are a great opportunity for somebody to step up."
General manager Jon Daniels admitted the Rangers may have to consider trade possibilities. Their focus in that area had been on the bullpen, but that could change.
"Maybe," Daniels said. "We'll take a step back and assess where we are at. We still have a lot of confidence in our pitching staff."
The Rangers aren't sure who will fill in for Lewis. Right now, the Rangers are planning to pitch right-hander Nick Martinez on Friday, A.J. Griffin on Saturday and Martin Perez on Sunday against the Red Sox. Griffin will be making his first start since May 7 after missing six weeks because of shoulder inflammation and his return couldn't come at a better time.
Griffin was 3-0 with a 2.94 ERA in six starts and has made three starts on a rehab assignment. He pitched for Double-A Frisco on Sunday against Midland, going five innings, allowing two runs on three hits, two walks and seven strikeouts. He threw 77 pitches.
"It has been really good," Griffin said. "The first couple of rehab outings, you're just trying to find your delivery and iron your stuff out. The last outing, everything was super, pitches were better, results were better, I felt a lot better. I wasn't fighting myself."
Cole Hamels will likely pitch Monday on four days' rest, leaving the Rangers needing a starter for Tuesday. The club could bring Cesar Ramos out of the bullpen, and it still has Chi Chi Gonzalez and veteran right-hander Kyle Lohse at Triple-A Round Rock. Lohse, who signed a Minor League contract in May, is 2-4 with a 5.09 ERA in seven starts. He is not on the 40-man roster, and right now, that is at the maximum 40 players.
"All the evaluations have been OK," Banister said. "He could be one of the guys if needed. There are still roster implications for guys not on the roster. It's a situation that needs to be talked about, because if it's a roster situation, you could be cutting into your depth in other areas."
Darvish is not an immediate option since he is on the disabled list with tightness in his right shoulder and hasn't pitched since June 8. Darvish has not yet thrown off a mound, but he did have a productive long-toss session with pitching coach Doug Brocail on Wednesday.
"He threw well today on flat ground," Brocail said. "We'll see how he feels tomorrow and Friday, maybe throw a bullpen [session] on Saturday and go from there. He was really good today. My hand is still paying the price."
Brocail said Darvish has taken to a mechanical adjustment that will help his follow through and take pressure off the shoulder.
"I don't know if he's ready, but he's getting closer," Brocail said.
Darvish will likely need either a simulated game or at least one start on medical rehabilitation assignment before he returns to the rotation.
"It depends on how the bullpen goes," Brocail said. "It's also good to listen to what he has to say. If he feels it's all behind him, he'll have some say in this."
• Pitcher Mike Matuella, who was taken in the third round of the 2015 Draft out of Duke University, has a sprained ligament in his right elbow and has been shut down for the year. He made just one start for Class A Spokane after a 14-month recovery from Tommy John surgery.
• The Rangers have signed four more Draft picks: outfielder Kobie Taylor (15th round) from Portsmouth (New Hampshire) High School, right-handed pitcher Scott Engler (16th) from Cowley County (Kansas) Community College, left-handed pitcher Kenneth Mendoza (24th) from Clearview (New Jersey) High School and right-hander Tyree Thompson (26th) from Edna Karr (Louisiana) High School.