Hoping to rebound from their loss in Kansas City, the 49ers went home for Week 5 as they played a Bay Area battle with the Oakland Raiders. The Niners drew first blood with QB Alex Smith throwing a 4-yard TD pass to WR Arnaz Battle, yet the Raiders would respond with kicker Sebastian Janikowski getting a 33-yard field goal for the first quarter. In the second quarter, things started to look grim, as Oakland took the lead with Janikowski kicking a 36-yard field goal, while QB Andrew Walter threw a 22-yard TD pass to WR Randy Moss. In the third quarter, the 49ers would rebound, as Smith hooked up with Battle again for a 6-yard TD pass. Later, Alex would throw a 33-yard TD pass to RB Maurice Hicks, giving San Francisco the lead. In the fourth quarter, the 49ers continued to roll, as kicker Joe Nedney kicked a 19-yard field goal, while rookie DE Melvin Oliver returned a fumble 12 yards for a touchdown. The Niners would allow one last touchdown from the Raiders, in the form of QB Marques Tuiasosopo completing an 8-yard pass to TE Courtney Anderson, but Nedney would help the Niners get win #2 with a 39-yard field goal. This beating of their Cross-bay rivals would bring the 49ers to a 2-3 record

Based on the above article, answer a question. Who did the 49ers lose to before playing this game in Week 5 of the season?
Kansas City