The Raiders began their season with a Week 1 AFL Legacy duel against their AFC West rival, the San Diego Chargers, in the second game of an MNF doubleheader.  In the first quarter, Oakland got off to a surprising good start.  While the defense (led by newly acquired defensive lineman Richard Seymour) kept the Chargers offense in control, the Raiders offense struck first with running back Michael Bush getting a 4-yard touchdown run.  San Diego would respond in the second quarter as running back LaDainian Tomlinson got a 1-yard touchdown run.  Oakland would answer with what looked like a 19-yard touchdown pass to rookie wide receiver Louis Murphy, but was overturned as he was unable to get full control of the ball.  The Raiders would have to settle with kicker Sebastian Janikowski making a 37-yard field goal, while the Chargers closed out the half with kicker Nate Kaeding getting a 47-yard field goal. After a scoreless third quarter, Oakland regained the lead as Janikowski nailed a 35-yard field goal, but San Diego answered with quarterback Philip Rivers completing a 15-yard touchdown pass to wide receiver Vincent Jackson.  Afterwards, the Raiders got the lead again as quarterback JaMarcus Russell completed a 57-yard touchdown pass to Murphy.  However, the Chargers came right back as running back Darren Sproles got a 5-yard touchdown run.  Oakland tried to rally, but an interception ended all hopes of a comeback. With the tough loss, the Raiders began their season at 0-1.
Question: How many touchdown passes did Rivers throw in the fourth quarter?
Answer: 1