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8/25/2013 2:19 P.M. ET

Washington, teammates stand by struggling Scheppers

CHICAGO -- The Rangers aren't at all concerned about right-handed reliever Tanner Scheppers, who surrendered Josh Phegley's walk-off single in Saturday night's 3-2 loss to the White Sox at U.S. Cellular Field.

Rangers manager Ron Washington and catcher A.J. Pierzynski both backed the righty -- a key cog in the Rangers bullpen this season -- after the game, and Washington did so again Sunday morning before the teams' series finale.

"He just didn't execute. It's that simple," Washington said.

One thing Washington said the 26-year-old needs to improve on, however, is his breaking ball.

Although Scheppers relies heavily on his fastball -- which he throws 82 percent of the time (sixth-most among Major League relievers), according to fangraphs.com -- it is relatively flat with little movement. So even though it averages 96.1 mph and is tied for the ninth-fastest average fastball velocity in the Majors -- both according to fangraphs.com -- batters know what is coming and can react.

But if Scheppers can hone his breaking ball and consistently get it over even a handful of times in an inning, it puts at least the thought in the back of hitters' heads.

"If he shows me I can get the breaking ball over, then that will put a doubt in their mind," Washington said. "But it's all about executing the fastball, too."

And that, more than anything, has led to Scheppers' recent struggles, as he has blown a save and taken a loss in his last two appearances.

"He's never been a strikeout guy, so there's going to be contact," Washington said. "They're making contact and they're putting the ball in play and they're finding holes. He's just got to execute pitches better."

Martin hopes to return as soon as Monday

CHICAGO -- Leonys Martin was out of the lineup for the Rangers' series finale Sunday against the White Sox, but Martin and the Rangers are hopeful the center fielder will return to the field Monday night in Seattle.

Martin sprained his right ankle in Saturday's 3-2 loss when he and left fielder David Murphy collided in shallow left-center field while going for a fly ball off the bat of Paul Konerko.

Martin was helped off the field and received X-rays, which were negative, and the 25-year-old was moving around the clubhouse fine Sunday morning.

"I'm going to get all the treatment that I can today, and I want to get ready for tomorrow," Martin said.

That was also the expectation of Rangers manager Ron Washington, though the play -- and Martin's reaction -- looked bad.

Neither Martin, shaded toward right-center, nor Murphy initially heard the other call for the ball, which Murphy caught. Murphy said he heard Martin just as the ball was falling into his glove, but said it was too late to back away. Martin, focused on the ball, ran into Murphy, flipped sideways and twisted his ankle while falling to the ground, where he rolled around in pain until he was attended to.

Said Martin: "When I collided, I hurt so badly I thought I broke something."

It turned out to be nothing more than a sprain for the youngster, who is putting together a solid year in his first full Major League season. Martin is hitting .271/.328/.389 with six home runs, five triples and 29 stolen bases and has progressively improved, leading Washington to dub Martin the club's most improved player since Spring Training.

"He's come a long ways. But he's still got a long ways to go," Washington said. "It'll probably be another three years before you see his full potential. In his whole career he's never played controlled baseball; he's played out of control."

That's beginning to turn around as of late, as Martin has not only played better, but smarter.

"He's doing a lot of the right things," Washington said. "It took a while. He's getting better. From February to now? Jesus. All the issues we had with him in April and May and June, he's come a long ways."

Worth noting

• Right-hander Yu Darvish was fine Sunday morning after dealing with cramping in both legs Saturday, Rangers manager Ron Washington said. Washington said Darvish initially experienced the cramping in the seventh after striking out Dayan Viciedo with runners on the corners for the first out of the inning.

A horde of Rangers staff visited the mound two batters later, when Darvish stumbled after a pitch in the dirt to Alejandro De Aza. Darvish then disclosed the cramping to Washington, but remained in the game until getting De Aza to pop out two pitches later.

Darvish walked slowly off the mound and Washington said the cramping again caught his legs just as he got to the dugout steps. It is considered a non-issue and Darvish expects to make his next start.

• Darvish struck out 11 batters in Saturday's no-decision, his 10th game of at least 10 strikeouts this season. It is the first time a Rangers pitcher has struck out 10 or more batters 10 times in a season since Nolan Ryan (18 in 1989) and the first time a Major League pitcher has hit the mark since 2004 (Randy Johnson, 13, Johan Santana, 12).

Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.