Hoping to rebound from their divisional road loss to the Browns, the Ravens flew to Bill Walsh Field at Monster Park for an interconference duel with the San Francisco 49ers. Baltimore would even go up against the QB that helped them win Super Bowl XXXV, Trent Dilfer, because QB Alex Smith was out with a separated shoulder. After a scoreless first quarter, the Ravens got the first punch with kicker Matt Stover getting a 26-yard and a 32-yard field goal. In the third quarter, Stover gave Baltimore a 49-yard field goal. However, the 49ers threatened with Dilfer completing a 23-yard TD pass to WR Arnaz Battle. The 49ers' kicker Joe Nedney missed the potential game-winning field goal from 52 yards out, and the Ravens held on for the lead.

Based on the above article, answer a question. Which player was replacing Alex Smith due to injury?
Trent Dilfer