To replace Betancourt on the active roster, the Indians called up right-hander Brian Slocum from Triple-A Buffalo.
Betancourt, meanwhile, will be resting the injury for a little while before beginning the rehab process. He's already back in Cleveland.
"We'll keep him out of action for a period of about seven to 10 days," Soloff said.
Soloff said an injury to the lat is neither common nor uncommon in pitchers. The muscle, he said, is pivotal in a pitcher's delivery.
"It's a very broad muscle in the back," he said. "It accelerates the arm's throwing motion."
Though the 30-year-old Betancourt has been on the DL twice before, this is the first time he's suffered an injury in this particular area.
In a team-high eight appearances this season, Betancourt has no record and a 6.43 ERA, striking out six and walking one.
The big call:
Slocum was in uniform and ready for Buffalo's 1:05 p.m. ET game against Richmond on Thursday when manager Torey Lovullo called him into a corner of the dugout and went to give him a hug.
The 25-year-old Slocum could hardly believe his eyes.
"Right away," he said, "I tried to pack as fast as I could and threw on a suit."
Unfortunately, he had no time to shower.
"I was feeling pretty grimy by the time I got here," he said.
That's OK, though. The showers are pretty nice at the Tribe's team hotel in the ritzy Plaza section of Kansas City.
Slocum last pitched Wednesday, so his arm was fresh and ready to help out Friday against the Royals. In five appearances for the Bisons, he has gone 0-0 with a save and a 1.93 ERA.
A second-round pick in the 2002 First-Year Player Draft, Slocum was converted to the relief role at the end of 2005 before heading off to the Arizona Fall League, where he went 2-1 with a 3.15 ERA in 11 appearances.
His clubhouse claim to fame during Spring Training was that he quickly established himself as the go-to team barber.
"Two guys have already asked me for a haircut," he said before Friday's game.
Here's the question:
Can you guess which Indians pitcher has the club record for most strikeouts over the course of three consecutive games? Can you guess the total and the year in which the feat was accomplished?
The Indians already have a room reserved for right-hander Jeremy Guthrie at the team hotel, so another move could be coming any day now.
"You might run into him," manager Eric Wedge said with a laugh about Guthrie.
The Tribe's injury-depleted and poor-producing bullpen has necessitated quick changes, and Guthrie, the team's No. 1 pick in the 2002 First-Year Player Draft who owns a 2-0 record and 1.00 ERA in three starts at Buffalo this season, figures to be a welcome addition.
"It's the best he's pitched in his career with us," general manager Mark Shapiro said of Guthrie's start. "Now's the right time to bring him in."
Shapiro and Wedge both hinted that the stay of Rafael Perez, who was called up Thursday when Miller went on the DL, might be a short one. Perez, though, impressed when he quickly set down the side in one inning of work against the Orioles on Thursday.
"He threw the ball well," Wedge said. "He has a live fastball and slider."
With Fernando Cabrera (bruised right heel) eligible to come off the DL on April 29, the bullpen figures to be in flux throughout the next few days.
"This is where our depth comes into play," Wedge said.
Down on the farm:
Buffalo first baseman Ryan Garko is day-to-day with a bruised left wrist after getting hit by a pitch
on Wednesday. X-rays were negative. Garko, a converted catcher, is batting .346 with a home run and 15 RBIs this season. ... Cabrera pitched 2 1/3 scoreless innings to get the victory in a rehab appearance with the Bisons on Thursday. Outfielder Jason Cooper was 2-for-3 with a walk and two runs scored. ... Double-A Akron right fielder Brad Snyder has hit in 12 of his last 14 games and reached safely in 14 straight.
The Indians do not have a first-round pick in the June draft. Their first-round selection was awarded to the Angels as compensation for the free agent signing of Paul Byrd. The Tribe will, however, have five out of the first 75 picks (Nos. 39, 56, 57, 69 and 75). ... The Indians' four, five and six hitters are hitting a combined .379 (74-for-195) with 48 runs, 15 home runs and 43 RBIs. ... The Indians came into this three-game series with KC having won 10 of their last 11 games against the Royals.
And the answer is:
Luis Tiant struck out a club record 41 batters over the course of three straight starts in 1968. He fanned
nine on June 23, 13 on June 29 and 19 on July 3.
The Indians and Royals continue the series with Saturday's 7:10 p.m. ET game at Kauffman Stadium. Byrd (2-1, 7.02 ERA) will get the start opposite right-hander Joe Mays (0-1, 11.68