Blum drove in the winning run in the Astros’ last at-bat for the third time this season - he did it in consecutive games against the Chicago Cubs in June. Houston won for the ninth time in its last at-bat.
Michael Bourn drove in three runs and also assisted on two putouts at the plate to help the Astros reach .500 for the first time since they were 1-1 on April 7.
Oswalt allowed three runs and five hits before leaving in the seventh with numbness in two fingers in his right hand.
Tejada led off the ninth with a single against Joe Beimel (0-5), who retired Lance Berkman before being replaced by Mike MacDougal. Tejada moved up on Carlos Lee’s flyout to center and Hunter Pence was walked intentionally.
MacDougal struggled with his control after putting Pence on, throwing a wild pitch and walking Ivan Rodriguez before Blum singled to right to end the game.
Beimel also gave up Jeff Keppinger’s tying sacrifice fly in the eighth. Blum helped set up the run when he doubled after the Nationals misplayed his foul pop earlier in the at-bat.
Jeff Fulchino (3-3) got the win with some help from Bourn in the ninth. Nyjer Morgan hit a one-out single to center with Willie Harris on second, but Bourn made a perfect throw to the plate to keep the game tied at 5.
Cristian Guzman’s two-run single off Chris Sampson put the Nationals ahead 5-4 in the seventh.
Lee and Bourn hit leadoff homers in the second and third off Scott Olsen to put Houston up 2-0.
Oswalt needed only 38 pitches to retire the first nine batters he faced. Morgan led off the fourth with a single to right, then stole second and third. He scored on Nick Johnson’s one-out double to left-center to cut the Astros’ lead to 2-1.
Johnson tried to score on Adam Dunn’s single to center, but Bourn threw him out at home.
Bourn drove in two more runs with a single in the fourth. Blum led off with a walk and Kaz Matsui singled before Oswalt advanced both runners on a sacrifice.
Oswalt retired seven of eight hitters before running into trouble in the seventh.
Dunn and Josh Willingham led off with back-to-back doubles and pitching coach Dewey Robinson came out to check on Oswalt. A trainer and manager Cecil Cooper jogged to the mound and Oswalt left after a brief discussion.
