HOUSTON -- Until signing with the Astros, veteran Darin Erstad had played in the big leagues for 13 years, all as a starter.

He signed on with Houston as a backup, knowing he was joining an outfield occupied by three players who wouldn't need many days off.

The transition has been complicated. The 33-year-old former Gold Glove winner has an entirely different pregame routine, and he's still acclimating himself to his new role.

"You do the same thing for several years, and then all of a sudden you don't anymore," Erstad said. "I'm just playing with some stuff, trying to figure it out. But I understand my role here. I'm just here to help. When a guy goes down, I'll step in and try to help the team."

Erstad received the start on Tuesday, in place of Michael Bourn, who tweaked his groin during the series opener with the Padres. If Bourn needs more than one day to heal, Erstad can count on being in the starting lineup again.

Erstad has played in every game but three so far this season, but he's only started four times. He was hitless in his first three at-bats Tuesday, but he jumped into the late-game hit barrage, singling in the seventh and doubling home a run in the eighth.

Pitching matchup
HOU: RHP Chris Sampson (0-2, 8.74 ERA)
Sampson had the shortest start of his career in his last game, lasting just two-thirds of an inning in an 11-5 loss to Colorado on Friday night. The right-hander changed his pregame routine and also was coming off the flu and a long layoff. He may have been too strong, as most of his pitches were up in the zone. Sampson said he would go back to the drawing board before his next start. He's pitched well against Cincinnati, going 1-0 with a 2.93 ERA in 15 1/3 career innings. That includes allowing two earned runs in a seven-inning start at Great American Ball Park last year.

CIN: RHP Bronson Arroyo (0-2, 5.48 ERA)
Arroyo pitched 5 2/3 innings and allowed five runs -- four earned -- on eight hits with three walks and four strikeouts in a 5-2 loss to the Brewers on Friday. High pitch counts continually have marred his outings. He threw 26 first-inning pitches before finishing with 116. Arroyo also is putting the leadoff batter on base a lot. He did it in four of the six innings he pitched on Friday.

Tidbits
Jack Cassel will be called up in order to start Thursday in Cincinnati. The Astros will make a corresponding move prior to that game to make room for Cassel on the roster, but Houston manager Cecil Cooper did not give any indication as to which current player will be removed. ... The Astros will play in three times zones during their upcoming road trip: Eastern (Cincinnati), Central (St. Louis) and Mountain (Arizona). The Astros are in the midst of playing 12 of 17 and 22 of 33 away from home. ... The Astros have scored 20 runs in the first inning, their most in any inning this season.

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 MLB.TV
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Up next
• Thursday: Astros (Jack Cassel, 0-0, -.--) at Reds (Johnny Cueto, 1-1, 3.42), 11:35 a.m. CT
• Friday: Astros (Shawn Chacon, 0-0, 2.77) at Cardinals (Braden Looper, 3-1, 5.49), 7:15 p.m. CT
• Saturday: Astros (Roy Oswalt, 2-3, 6.00) at Cardinals (Adam Wainwright, 2-1, 2.73), 12:10 p.m. CT