"He made me two nasty pitches before that," Kotsay said. "But then he threw me a slider that just kind of spun."
Kotsay was in the leadoff spot for the first time since his return since back surgery and responded with four hits.
"We had a couple guys out, and he's been swinging the bat well the last couple of days," A's manager Bob Geren said. "And he swung the bat well again tonight."
"I do like hitting here," Kotsay said of Minute Maid Park. "It has a great backdrop and I've had some good success here. I got some good pitches tonight."
But with the potential winning run on third with nobody out, the A's couldn't get him home.
Mark Ellis followed Kotsay's home run with a double, then moved to third on a Lidge wild pitch, but the righty was able to strike out Nick Swisher and Eric Chavez, then got Bobby Crosby to pop up to end the inning.
Swisher and Chavez went a combined 0-for-11 and left eight runners on base.
"They had a couple of situations where they normally get it done," Geren said. "They just didn't get it done tonight."
The Astros would score the winning run in the 11th inning when Brad Ausmus singled off Ron Flores (0-1) to score Adam Everett, who beat the throw from Jason Kendall in left field.
"If the hop had been true bounces, I would have had a better chance," Kendall said. "The ball snaked on me a little bit. I was more worried about fielding it cleanly, and I just threw it a little bit too far left."
Kendall, batting eighth, doubled in the 10th, and Geren brought backup catcher Kurt Suzuki off the bench to pinch-hit for the pitcher's spot. After the inning, Suzuki went behind the plate and Kendall went to left.
Kendall played 27 games in the outfield with Pittsburgh in 2001, and there is an old baseball axiom that the first ball will find you when you are in a foreign position.
The first ball in the bottom of the 10th was a fly ball off the bat of Orlando Palmeiro that Kendall handled perfectly.
"I definitely feel a little more comfortable with catcher's gear on," Kendall said.
"It'll find you every time," said Kotsay. "But I had him in the right spot."
"I just wasn't going to let him Kelly Leak me on anything," Kendall responded, referring to the "Bad News Bears" center fielder who tried to catch any ball hit in the air.
The move may have saved the game temporarily in the bottom of the 10th, when the Astros had the bases loaded with two outs. Suzuki showed great quickness behind the plate in bouncing up from behind the plate and fielding a dribbler off the bat of Morgan Ensberg, just getting him at first base.
The A's had won eight of their last nine and their starting pitching had been dominant during that stretch, but all it took was this Interleague series opener to put that all to rest.
Leading 3-2 in the fourth inning, starter Joe Kennedy gave up a two-run home run to Ausmus on an 0-2 pitch, giving the Astros a 4-3 lead and ending a long streak for the A's starting pitchers.
Geren said he thought it wasn't that bad of a pitch from where he was, but Kennedy thought differently.
"Obviously, it wasn't a good pitch because it went over the wall," Kennedy said. "It was an 0-2 curveball that I tried to bounce."
Ausmus was able to hook it around the foul pole down the left-field line, which is only 315 feet away from home plate.
"That's part of their home-field advantage," Kennedy said.
That swing ended a streak of 13 games in which the A's starting pitchers had allowed two earned runs or fewer. It was the third-longest streak in A's history.
Kennedy lasted just five innings, his first start since the end of April in which he has gone fewer than six innings.
Kennedy helped his own cause from the batter's box in the second inning, coming up with a two-run double.
Dan Johnson walked to start the inning, then with two outs Kendall singled. Astros pitcher Roy Oswalt may have thought he would be out of the jam because he was facing a pitcher, an American Leaguer at that.
But Kennedy took an 2-0 pitch and smacked a double that plated both runs. He came around to score after consecutive singles by Kotsay and Ellis.
Oswalt settled in after that second inning, allowing just two more runners to reach base. He struck out 10 over six innings and retired the A's in order in the fourth, fifth and sixth innings.
The A's had a chance in the seventh after Chad Qualls came on in relief and gave up a single to Kotsay, then after getting an out he walked Swisher.
Trever Miller then came out of the Houston bullpen and he was able to get the next two outs with no further damage.