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8/19/2014 7:15 P.M. ET

Next Tuesday too optimistic a target date for Yu

MIAMI -- The Rangers are backing off the idea of Yu Darvish returning to the rotation and pitching next Tuesday against the Mariners.

Darvish is on the disabled list with inflammation in his right elbow, and he has not thrown a baseball since he tried to play catch a week ago in Arlington. Darvish did not travel with the Rangers for their two-game series with the Marlins.

Darvish made his last start on Aug. 9, and was eligible to come off the DL next Monday. It doesn't appear he will be ready that quickly, and Darvish has already made it clear that he doesn't want to do anything that will jeopardize his long-term future.

"I don't know what is going to happen," manager Ron Washington said. "We'll just have to wait and see."

The Rangers could bring back Robbie Ross from Triple-A Round Rock to pitch against the Mariners or they could bring Scott Baker out of the bullpen. Baker has made four starts for the Rangers this season, with the last one coming on July 13, when he threw 77 pitches against the Angels.

Texas outfielders accept Ice Bucket Challenge

MIAMI -- Ice bucket mania is sweeping through the Rangers' clubhouse.

Rangers outfielders Leonys Martin, Alex Rios and Shin-Soo Choo were the latest to get doused by ice water on Tuesday in the dugout at Marlins Park. They were challenged by none other than Choo's 9-year-old son, Alan.

"He challenged the Rangers outfielders," Choo said. "I told him I was a DH."

Apparently that doesn't work at a National League Park. They don't use the designated hitter there.

"It was cold, but it was for a good cause," Rios said. "Whatever it takes."

The Ice Bucket Challenge has gone viral this summer on social media in support of research for amyotrophic lateral sclerosis. The ALS Association announced on Monday that $15.6 million has been raised through the Ice Bucket Challenge. Last year, $1.8 million was raised during the same time period (July 29-Aug. 18).

According to the unofficial rules, once somebody has been doused with ice water, they have the right to challenge others. Once somebody has been challenged, they have 24 hours to accept it or make a donation to charity.

Rios challenged trainer Kevin Harmon, Martin did so with Elvis Andrus and Choo challenged a photographer from Korea.

Rios a late scratch with bruised right thumb

MIAMI -- Outfielder Alex Rios was scratched from Tuesday's lineup after batting practice because of a bruised right thumb. Rios has already been dealing with a sprained right ankle, but apparently the thumb has been bothering him as well.

Rios has six hits in his last 49 at-bats and is hitting .219 in his last 52 games, as his batting average has dropped from .335 to .284. That's his lowest average since he was hitting .276 on April 16. Rios leads the American League with eight triples, but hasn't hit once since June 9.

With Rios out, Shin-Soo Choo started in right field and Jim Adduci was inserted into the lineup in left. There is no designated hitter being used in the National League park.

Prospect Knebel shut down with elbow sprain

MIAMI -- The Rangers are shutting down right-handed reliever Corey Knebel for the remainder of the season because of a sprained right elbow. Knebel will be down for six weeks and be re-examined at the beginning of October. If all goes well, he will begin throwing in November.

Knebel was one of two pitchers acquired from the Tigers for reliever Joakim Soria. Knebel was 1-0 with a 3.75 ERA in nine games at Triple-A Round Rock and was a candidate to be called up in September. He pitched in eight games for the Tigers earlier this season.

The Rangers also announced that pitcher Wilmer Font underwent arthroscopic surgery to remove a bone spur in his right elbow. Font, who pitched in five games for the Rangers in 2012-13, is expected to be ready for Spring Training 2015.

The Rangers are also shutting down right-hander Akeem Bostick because of a groin injury. He was their second-round Draft pick from West Florence High (S.C.) last year. Bostick was 5-6 with a 5.17 ERA in 21 games at Class A Hickory.

In other Minor League pitching developments, the Rangers are serious about taking a hard look at Lisalverto Bonilla as a starter. Bonilla, who was acquired from the Phillies in 2013 in the Michael Young trade, has been a reliever for most of his career. But he has made four starts at Round Rock and has a 3.37 ERA in those games.

"He has three above-average pitches," farm director Mike Daly said. "We have a lot of right-handed relievers. We have a need for a starter and he has been interesting."

Worth noting

• Don Welke, who has spent eight seasons with the Rangers, is leaving the organization to join A.J. Preller with the Padres. Preller was hired by the Padres as their general manager earlier this month, and there are significant restrictions as to who he can hire from the Rangers.

But Texas did give him permission to hire Welke, who was one of Preller's early mentors when they were with the Dodgers. Welke had been working for the Rangers under the title of special assistant to the GM, but he was involved in all areas of scouting both amateur and professional.

Welke was among the scouts sent to Japan to watch Yu Darvish pitch. He also was instrumental in the acquisition of Josh Hamilton, Cliff Lee and Adrian Beltre, and the amateur signings of Jurickson Profar, Martin Perez, Jorge Alfaro and Luis Sardinas.

• Outfielder Engel Beltre, who has been out all season while recovering from a broken bone in his left leg, has been recalled from his medical rehab assignment because of continued soreness. He will be examined further by Dr. Keith Meister later this week.

• Double-A Frisco outfielder Nomar Mazara was named the Texas League Player of the Week after going 8-for-22 with two home runs and six RBIs.

• Outfielder Jamie Jarmon, who was the Rangers' second-round pick in the 2012 First-Year Player Draft, has left the organization to play college football at the University of Delaware.

• Marlins Park is the 48th ballpark the Rangers have played in since 1972. They have now played in all the current parks.

T.R. Sullivan is a reporter for MLB.com. Read his blog, Postcards from Elysian Fields, and follow him on Twitter @Sullivan_Ranger. This story was not subject to the approval of Major League Baseball or its clubs.