Hanson had been overpowering for eight innings, striking out seven and allowing five singles and no walks in his longest major league outing.
So Houston felt it had a chance when closer Rafael Soriano (1-5) entered to try to get the save.
Tejada admitted he was glad to not have to face Hanson.
"Not just me," Tejada said. "Everybody was. The way the game was going, the way he was pitching, we weren't doing much.
"The kid is unbelievable. He pitched a great game. I just tried to hit the ball up the middle with the bases loaded. That's what I do best."
Astros manager Cecil Cooper was another person happy that Hanson was out of the game.
"We probably wouldn't have gotten anything off of him," Cooper said. "It didn't look like it. We had chances and we didn't really do anything against him. That kid's pretty impressive."
The Braves, who have lost six of seven, were stunned.
"It [the loss] was awful the way he pitched," Atlanta manager Bobby Cox said. "He pitched terrific baseball. He had everything going.
"Hanson was right at 100 [pitches]. He wanted to go back out and could have come back out. But you have to be careful. You always want to start your closer with a clean inning. You don't want him to come in with men on. And we've got confidence in him."
Hanson was pragmatic about the loss.
"That's just the way it goes sometimes," he said. "We did a good job of keeping runs off the board. That's just baseball.
"Everything felt really good. I would definitely say that was one of my better starts."
Hanson would have liked to go one more inning.
"I understood the situation [in the ninth] 100 percent," he said. "He's the manager and I do what he says. Every start, I want to go back out. [Cox] is the one who decides when I come out of the game. That's the way it goes."
Jose Valverde (4-2) struck out two in a perfect ninth for the win.
Houston's Wandy Rodriguez went seven innings, allowing one run and three hits, striking out six.
Rodriguez, who retired 10 of 11 hitters from the second through the fifth innings, has limited opponents to one run or less in 11 of his last 13 starts.
- Astros 3B Geoff Blum left the game in the third inning with a contusion to his right lower leg and a mild ankle sprain. He was injured sliding into second base. Chris Johnson made his major league debut replacing Blum.
- It was the fifth straight game decided by one run for Houston. The Astros are 4-1 in the games.
- The Braves are 24-21 in one-run games after going a majors-worst 11-30 last season.
- The Braves have had 84 quality starts, nine more than all last season.