HOUSTON -- A day after throwing 43 pitches in two innings against the Rockies on Wednesday, Nationals reliever Julian Tavarez was given the day off on Thursday, and it came at a good time.

Tavarez has not pitched well this month, allowing four runs in three innings. What bothers manager Manny Acta the most is that Tavarez is walking too many people. For the season, Tavarez has 26 walks in 34 1/3 innings.

"He has been very inconsistent for the last few outings," Acta said. "He is walking way too many guys. He is pitching behind in the count. He can't afford to do that. I don't think he is tired. He is pitching like everybody else. He is in tremendous shape and works very hard."

Tavarez was seen working out with his dumbbells on Thursday afternoon. He said he doesn't know why he is struggling right now.

"Things have to turn around -- I have to go day by day," Tavarez said. "I'm surprised [I'm waking a lot of batters]. I'm missing my spots. But things will change. You have to go day by day. "

Pitching matchup
WSH: LHP Scott Olsen (2-4, 6.04 ERA)
Olsen came within one out of pitching the first complete game of his career and helped the Nationals defeat the Braves, 5-3, at Nationals Park on Sunday. Olsen gave up three runs on eight hits in 8 2/3 innings. He also went 2-for-3 and drove in a run. With two outs in the ninth inning, the Braves' Nate McLouth hit a two-run homer that knocked Olsen from the game after 116 pitches.

HOU: RHP Roy Oswalt (5-4, 3.81 ERA)
Oswalt has regained his dominating form, going 3-1 with a 2.13 ERA in his past five starts. He threw a two-hitter on June 29 at San Diego and allowed one run on a wild pitch, then he held the Giants to three hits and one run in his last start, on Sunday in San Francisco. Oswalt is 3-1 with a 2.97 ERA in 11 career games (nine starts) against the Nationals. He allowed four runs on four hits in five innings in Washington on May 5 in a game that was suspended because of inclement weather.

Tidbits
Reliever Joe Beimel has a 1.04 ERA in his past 20 appearances. ... Outfielder Austin Kearns has 16 plate appearances in his past 19 games. ... Shortstop Alberto Gonzalez is 17-for-50 [.340] since being recalled from Triple-A Syracuse on May 30.

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Up next
• Saturday: Nationals (Craig Stammen, 1-4, 4.88) at Astros (Mike Hampton, 5-5, 4.16), 7:05 p.m. ET
• Sunday: Nationals (Jordan Zimmermann, 3-3, 4.52) at Astros (Brian Moehler, 5-5, 5.52), 2:05 p.m. ET
• Monday: Off day