HOUSTON — The Houston Texans have consecutive wins for the first time this season.

Never mind that they almost let this one slip away with a poor second half.

Steve Slaton scored two touchdowns and the Texans built a big lead before holding on for a 24-21 win over the San Francisco 49ers yesterday.

The Texans (4-3) led 21-0 at halftime, then withstood a rally led by backup quarterback Alex Smith. Eugene Wilson's interception on fourth down halted the 49ers' last-gasp drive.

"We get down, they get up and they all of a sudden grabbed the momentum of the game," Houston coach Gary Kubiak said. "But we made some big plays late and defensively Eugene made a big play so it was a big, big win."

San Francisco (3-3) benched Shaun Hill after a terrible first half, and Smith threw three touchdowns to tight end Vernon Davis to close the gap.

"I just thought it was time to make the switch," 49ers coach Mike Singletary said. "It was as simple as that. No long, drawn-out thought process. But let's make the change."

Singletary wouldn't say who would start next week.

Michael Crabtree started in his NFL debut and had five receptions for 56 yards. Singletary was pleased with Crabtree's performance.

"I was kind of calm," Crabtree said. "I practiced on getting calm and coming into the game, knowing what I was supposed to do and executing my plays. I think I did a good job, but I've got some more work to do."

Davis' third touchdown on a 23-yard reception got San Francisco within 24-21 with 3:49 remaining. Houston's only second-half points came on a 50-yard field goal by Kris Brown with about 7 1/2 minutes left.

Crabtree's first game after ending a 71-day contract holdout Oct. 7 was overshadowed by the quarterback shake-up. In his first game since 2007, Smith sparked San Francisco's offense in the second half and was 15 of 22 for 206 yards. The former No. 1 overall draft pick made only one major blunder — the desperation throw that Wilson picked off.

Hill finished just 6 of 11 for 45 yards.

Houston's Matt Schaub was 20 of 30 for 264 yards and two touchdowns.