Lewis started on opening day, and he ranks second among Texas starters with a 3.43 ERA in 16 outings, 15 of which came before a recent stint on the disabled list with what was announced as forearm tendinitis.
The right-hander returned Wednesday at Oakland and was effective for five innings, but his arm tightened up again and further examination showed a torn flexor tendon in his elbow. He'll have surgery later this week and is expected to miss at least nine months.
General manager Jon Daniels called it "a blow for us, but it's something we're going to recover from."
"It's an opportunity for someone to step up," he said. "I feel bad for Colby, he's been a warrior. He's pitched a ton of innings and he's been such a leader by example."
Assuming Texas (57-38) gets back to the playoffs, that may be when Lewis is missed most. He was 4-1 with a 2.34 ERA in eight postseason starts as the Rangers won back-to-back AL titles.
Perez (1-1, 5.54 ERA) has split his only two major league starts, posting a 3.18 ERA in place of Lewis earlier this season.
"The guy has proved he can pitch here, so we didn't hesitate to bring him back," manager Ron Washington said.
The left-hander may not be in the rotation for long, though. Daniels admitted the Rangers are investigating a trade market that may include a number of big-name starters.
"We've had guys out there looking and had conversations with clubs," Daniels said.
Another in-house injury replacement helped the Rangers win the series opener 9-1. With Roy Oswalt sidelined due to back stiffness, Scott Feldman held down Boston's lineup as the Red Sox lost a fourth straight game Monday.
Having allowed 37 runs during its skid, Boston (48-49) certainly has no sympathy for Texas' pitching woes. For the season, Red Sox starters rank 27th in the majors with a 4.89 ERA.
"Good pitching and timely hitting," manager Bobby Valentine said. "We're due for it."
The Rangers have taken full advantage, scoring 33 runs in winning all three 2012 meetings. Mike Napoli has four homers and 10 RBIs in those contests, giving him 15 homers in 28 games versus Boston since 2008.
Clay Buchholz (8-3, 5.19) has been a rare bright spot for the Red Sox lately, and he'll try to build on Thursday's strong outing against the Chicago White Sox. He allowed one run in eight innings before Cody Ross' three-run homer in the ninth gave Boston a 3-1 win.
The right-hander got off to a rocky start this season but has gone at least six innings in each of his last seven starts around a stint on the DL with esophagitis. He's 4-1 with a 2.63 ERA in that stretch.
"I feel pretty confident in most all of my pitches each time I go out," Buchholz told the Red Sox's official website.
He may not, however, be quite as sure of himself against the Rangers, who've beaten Buchholz the last three times they've faced him. Texas took him deep four times - Napoli once - in a 5-1 win in Arlington in the most recent matchup April 3, 2011.
- Boston Red Sox
- Colby Lewis