Coming off their impressive road win over the Bengals, the Texans went home for a Week 7 interconference duel with the San Francisco 49ers.  Houston would get off to a fast start in the first quarter as running back Steve Slaton got a 1-yard touchdown run.  The Texans would add onto their lead in the second quarter as quarterback Matt Schaub completed a 9-yard touchdown pass to Slaton and a 42-yard touchdown pass to tight end Owen Daniels. However, the 49ers began to rally in the third quarter with quarterback Alex Smith hooking up with tight end Vernon Davis on a 29-yard touchdown pass.  In the fourth quarter, San Francisco continued to catch up as Smith found Davis again on a 14-yard touchdown pass.  Houston would respond with kicker Kris Brown booting a 50-yard field goal.  The 49ers tried to come back as Smith connected again with Davis on a 23-yard touchdown pass, yet the defense halted San Francisco's rally.
Question: What was the longest touchdown pass that Smith thre in the fourth quarter?
Answer: 23-yard