Downs made his first major league appearance in the outfield Monday night and hit a tiebreaking homer in the eighth inning, lifting the Astros to a 3-2 win over the slumping Cincinnati Reds.
"I don't know if I thrive in those situations, but I like them," said Downs, who got the start in right. "You can turn the game around with one at-bat. It felt great."
Downs greeted Nick Masset (3-6) with a 362-foot leadoff drive to left, sending the Astros to their second straight win after a three-game losing streak.
"It was one of those at-bats where he left something out over the plate and I put the (bathead) through it," Downs said.
Downs, who has started at all four infield positions, has been working out in the outfield, manager Brad Mills said. He handled three chances flawlessly, including two fly balls.
"We watched him settle under those two fly balls, and he looked OK," Mills said. "Then he came up with the big home run in the eighth inning. That was huge."
Brandon Phillips hit a leadoff homer in the first for Cincinnati, which has lost four straight.
Six Houston pitchers combined for a four-hitter, and the Astros turned three double plays. Cincinnati collected 13 hits while being swept by Milwaukee in a weekend series.
"We hit the ball on the ground for some double plays at the wrong time," Reds manager Dusty Baker said. "We haven't hit very well the last three games."
Rookie David Carpenter (1-3) picked up his first career win by getting Phillips to ground into an inning-ending forceout with runners on first and second in the seventh.
"It was definitely a tough one," Carpenter joked about his one-batter win.
Phillips got the Reds off to a fast start, hitting his fifth homer in his last eight games and No. 17 overall. It was his second leadoff homer of the season.
Houston left-hander J.A. Happ settled down after the rough start, setting a season high with nine strikeouts in six innings. He allowed three hits and walked three.
"I felt like I was in a good comfort zone," said Happ, who has a 2.40 ERA in five starts since being recalled from Triple-A Oklahoma City on Aug. 26. "I was able to throw my off-speed stuff early, which makes my fastball better. I felt pretty good. It's good when you have confidence in your pitches. That's the difference between a solid and not-so-solid outing."
Travis Wood pitched five scoreless innings in a surprise start for the Reds. He allowed four hits, walked two and struck out two.
Wood was pressed into action when left-hander Dontrelle Willis was scratched for the second consecutive game because of back spasms.
The Astros tied it up against Logan Ondrusek in the sixth. With runners on first and second and none out, Downs hit a grounder to third that skipped past Frazier for an error that allowed J.D. Martinez to score. Jimmy Paredes loaded the bases with a bunt single, and Carlos Lee scored on Clint Barmes' grounder that Frazier corralled with a diving stop to his left.
Willis visited a chiropractor, but his back didn't improve enough for him to make the start. ... The Reds struck out 33 times against the Brewers over the weekend. ... A lingering right ankle injury might limit Reds 1B Yonder Alonso to pinch-hitting for the rest of the season. Alonso was hurt while playing left field in Chicago the first weekend of August, and it's gotten progressively worse. ... RHP Homer Bailey will try to set a single-season career high with his ninth win in his start on Tuesday against Houston. RHP Bud Norris, the Astros' scheduled starter, will be trying to avoid a career-high 11th loss.