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05/09/2013 7:44 PM ET

Stomach illness among Werth's ailments

WASHINGTON -- Nationals right fielder Jayson Werth has started taking antibiotics to treat a stomach illness that may be contributing indirectly to his ailing right hamstring, manager Davey Johnson said on Thursday. The team believes dehydration has been a primary factor in the muscle tightening and cramping over the past week.

Although he took normal batting practice, Werth was out of the lineup for the fifth straight game on Thursday, and he underwent an MRI on the hamstring. The results are not final, but Johnson did not sound worried and does not expect Werth to be placed on the disabled list.

"They put him on an antibiotic, and his MRI, I think in talking to Jayson, was OK," Johnson said. "[Team physician Dr. Wiemi Douoguih] really hasn't gone over it with a fine-toothed comb yet, but he's going to look at that and we'll know more. I imagine, hopefully, what [Werth's] on, he'll be good to go soon."

Following Thursday's series finale against the Tigers, the Nationals start a three-game home set against the Cubs on Friday. Johnson said following Thursday's 5-4 win that Werth was likely to sit out Friday's series opener.

Werth began feeling tightness in Atlanta on April 29, the same day he fouled a ball off his left ankle. In his only action since, on May 2, he left after five innings.

With Werth out, Johnson has been operating with a short bench. Tyler Moore started six of the past seven games before Wednesday, when Roger Bernadina got his fourth start of the year and first in left field.

Relievers trying to stay sharp despite inactivity

WASHINGTON -- Nationals manager Davey Johnson joked before Thursday's game about walking through the locker room and having his relief pitchers come up and introduce themselves. You could forgive the bullpen guys for thinking their skipper may have forgotten about them of late.

Entering Thursday, the Nationals' 90 1/3 relief innings were the fourth fewest in the Majors and second fewest in the National League, behind the Cardinals' 84. Thanks to Monday's off-day, Tuesday's rainout and some stellar recent work by the team's starters, several Washington relievers have seen little game action this month.

"It's a little more difficult to find the feel and stuff like that, but that's part of it. That's part of being down there," right-hander Ryan Mattheus said. "The starters have been throwing the ball well, going deep in games, so that's just kind of the nature of the beast. So you've got to work hard to do what you can in your throwing program. Definitely still getting my work in, but it's tough to find feel sometimes."

Mattheus and righty long reliever Craig Stammen both pitched on Friday, their only appearance since April 28. Lefty long man Zach Duke and righty Henry Rodriguez have yet to pitch since April 30, and even setup man Drew Storen has gotten the ball once since April 29.

"A lot of them are my long relievers, and that's a good sign," Johnson said. "The bullpen guys, I tell them all the time, 'When it rains, it pours out there, boys. So just make sure you get your throwing in.'"

Nationals relievers have played 10 to 15 minutes of catch every day since Spring Training, and Mattheus said Johnson is good at monitoring them to make sure they stay sharp. Over his three-year big league career, Mattheus has learned how to manage the irregular work.

"It's nice to get out there every day, every two days, have a day or two in between," he said. "But that's never going to happen consistently, so it's just part of being a reliever. There's times when we'll be in there day after day after day, and we'll be hoping for a day off. So you've got to take these as they come, as well."

Worth noting

• First baseman Adam LaRoche, mired in a bad slump for much of the season, went 2-for-3 on Wednesday, with a pair of singles to left field. But according to Johnson, going the opposite way isn't necessarily a sign that LaRoche is locked in at the plate.

"That's usually what everyone says, that when you have a problem, you go the other way," Johnson said. "But with him, he's a pull hitter. I think early on, when he was flying out to left, his timing was a little off. When he gets right, he's generally driving the ball to the right side."

Still, LaRoche entered Thursday 7-for-13 with two doubles and six walks during a five-game hitting streak.

"I like where he's at," Johnson said. "I think he's seeing the ball better. I think his timing's coming around."

• Bryce Harper's blast on Wednesday meant that the Nationals have homered at least once in 67 consecutive series, the second-longest active streak in the Majors, behind the Rangers (76). The last time Washington failed to reach the seats during a series was a four-game set against the Mets, Sept. 12-15, 2011, at Citi Field.

Andrew Simon is a reporter for MLB.com. Follow him on Twitter @HitTheCutoff. This story was not subject to the approval of Major League Baseball or its clubs.