Uehara missed time with a similar ailment in Spring Training and will be re-evaluated Sunday to determine the extent of the injury. And if he is out for any period of time, he'll cause a ripple effect in Baltimore's chaotic rotation, which has already seen Alfredo Simon, Mark Hendrickson and Adam Eaton removed.
"I don't think it is serious," manager Dave Trembley said. "But I'm sure I am going to be saying my prayers tonight and hoping it is not because he is so important to us. But we will see how he is tomorrow."
Uehara and Jeremy Guthrie are the only Orioles to make every rotation turn this season. The Japanese rookie had also completed five innings in all of his previous starts, making him the only Baltimore starter who could claim that. Now, if he misses a start, the club will have to find two replacements from its farm system.
"We'd have to adjust," said Trembley, addressing the worst-case scenario. "It would be tough losing a guy of that quality. Every time he goes out there, you count on him keeping the game close and giving you innings."
"He has been one of our best pitchers," Huff added. "He has given us quality start after quality start. We just haven't scored enough runs for him. He's been kind of a hard-luck guy, and I don't know what the situation is. ... If we lose him it would probably be a big blow, but it's the front office's job to figure it out."
The right-hander worked two scoreless innings before showing any hint of the injury, and it only became apparent toward the end of the third. Uehara wasn't able to cover first base on an infield hit in that inning, and he flexed the muscle a few times while facing his final batter of the evening.
Uehara spoke about the ailment after the game, saying that the injury felt more like a cramp than anything else. The 34-year-old also said he won't know if he'll miss a start until the medical staff checks him out.
"I didn't pull anything," Uehara said via interpreter Jiwon Bang. "I have a history of hamstring problems. It's been a long [relationship] in a sense, so I know when not to go out and pitch."
Uehara had every intention of continuing his outing Saturday night, but Trembley elected to play it safe and go to Brian Bass. Bass (3-1) worked three innings for Baltimore, getting the Orioles deep into the game. Matt Albers and Jim Johnson both pitched an inning, and George Sherrill worked the ninth for his ninth save.
The Orioles (18-25) took a one-run lead in the third inning on an infield single by Nick Markakis, and the Nationals (12-30) answered in the fifth with a solo home run by Cristian Guzman. Huff came up with two outs and a man on first in the seventh inning and tripled to left-center field to chase home the decisive run.
"Obviously, I'd rather be jogging than running three bags," Huff said. "The ball has to bounce off the wall. Adam Dunn has to chase it down after the guy falls down in center field. That's pretty much what has to happen."
And with that timely hit, the Orioles made up for a quiet night at the office. Baltimore tied a season low with three hits, and two of them came late in the game. Catcher Gregg Zaun doubled in the seventh and was thrown out on a fielder's choice at third, and then Huff tripled off Ron Villone to take the lead.
"Huff was the secret weapon tonight. He was up here hitting in the cage," Trembley said. "I thought we had one shot late in the game, so let's do it. Tonight was kind of a team game. You're not always going to get one aspect of the game vs. another. You got a timely hit with Huff. You got very, very good pitching [and] very, very good situational pitching. You got tremendous infield defense. All that adds up to winning the game."
Sherrill, meanwhile, has logged five straight saves and five straight outings without allowing a hit. Baltimore's win sealed the team's first winning series since taking two from Minnesota in the first week of May, and the Orioles will go for their first three-game sweep of the season in Sunday's series finale.