An MRI confirmed the tendinitis. He was given an injection on Monday and general manager Jon Daniels does not believe the injury is serious.
"He suggested it would be best for him to skip his next start," Daniels said. "And being that he only has two scheduled starts before the break, we decided to play it safe and shut him down for this 10-day period here before the All-Star break. Our expectation is that he should be able to bounce back and be activated after the break. Obviously, we'll take it step by step. But that's our expectation -- that he'll be back after the break."
Lewis started feeling tightness in his forearm the past two innings of his June 17 start against Houston, when he allowed only three hits and a run over seven innings in a victory. He felt fine in the early stages of Saturday's game against Colorado.
"Then it just kind of came on and progressively got tighter as the game went on," said Lewis, who gave up 12 hits and eight runs in four innings against the Rockies.
He added: "It's just one of those situations, better to be safe than sorry, and not push the issue now and not be able to be there for these guys at the end of the year. You have to listen to your body, and I'm not going to push it."
Lewis experienced something similar in 2008 when he was in Japan and after missing about 20 days, returned to the rotation and finished the season.
"It's the same sort of feeling I had in 2008. Maybe it just needs rest," Lewis said. "That's what I took off then, and I was able to bounce back and be fine, and I haven't had the issue since then. Maybe it was just throwing a lot of innings early. But it is what it is, and move on."
The club has not determined who will start on Saturday, which is Justin Grimm's spot. Grimm lasted just one inning (plus two batters) on Monday against the Detroit Tigers in his second start since coming up from Double-A Frisco.
Martin Perez, the 21-year-old left-handed starter called up from Triple-A Round Rock earlier on Tuesday, takes Lewis' spot on the roster. He could end up starting Saturday against Oakland, but it's also possible that Grimm makes that start. Daniels said bullpen needs the next few nights will help sort all of that out.
Lewis, 32, is the club's No. 1 pitcher this season and leads the club with 100 innings pitched. He is 6-6 with a 3.51 ERA with 90 strikeouts and just 12 walks. He has pitched at least 200 innings the past two seasons for Texas. Few pitchers in the league have logged more total innings in that time, if you include the playoffs. Lewis has been the club's top postseason pitcher during its two straight runs to the World Series, going 4-1 with a 2.34 ERA in eight playoff starts in 2010 and 2011.
Lewis is the fourth Rangers starter to get injured this season. Neftali Feliz (sprained elbow ligament), Derek Holland (stomach ailment, sore shoulder) and Alexi Ogando (strained groin) are currently on the disabled list. Holland is scheduled to make his first rehab start on Wednesday at Triple-A Round Rock and will make two starts, maybe three, before he's ready. Daniels acknowledged that Lewis' injury could mean that after two starts, Holland might get reinserted into the rotation prior to the All-Star break. But that will depend on how Holland is feeling after he makes two rehab starts. Feliz can't come off the 60-day DL until July 18.
The Rangers didn't make a 25-man roster move until Feliz's injury on May 21. But since then, they've had a rash of them. That includes reliever Koji Uehara, who is on the DL with a strained lat muscle.
Roy Oswalt was signed as an insurance policy and is in the rotation. Feldman, who just returned to the bullpen in favor of Grimm, now goes back to the starting staff and we'll see what the club decides on Grimm.
Daniels said his staff won't complain about the injuries, noting that none of them appear to be season-ending issues. Still, the injury bug vastly has altered the starting rotation.
"We went through April and May and I think we were literally the only club not to make a move," Daniels said. "It was borderline boring. We had nothing to do. They've been keeping us busy lately. You'd like not to.
"But fortunately, it doesn't appear that any of these are significant to where they're long term or threatening their availability to pitch later in the season. It's a test. We tried to build as much depth coming into the season continuing with the promotions and signing Roy. At this point, we're really glad we have those guys."
Information from The Associated Press was used in this report.