Coming off their divisional home win over the Jaguars, the Titans flew to Candlestick Park for a Week 9 interconference duel with the San Francisco 49ers.  Tennessee would trail early in the first quarter as 49ers kicker Joe Nedney got a 40-yard field goal, yet the Titans would answer with kicker Rob Bironas making a 21-yard field goal.  The Titans would take the lead in the second quarter as quarterback Vince Young got a 10-yard touchdown run, but San Francisco would close out the half with a 3-yard touchdown run from running back Frank Gore and a 12-yard touchdown pass from quarterback Alex Smith to wide receiver Jason Hill. In the third quarter, Tennessee would tie the game as running back Chris Johnson got a 1-yard touchdown.  The 49ers would retake their lead in the fourth quarter with Nedney nailing a 25-yard field goal, yet the Titans would regain the lead with Johnson's 2-yard touchdown run, Bironas' 28-yard field goal, and cornerback Cortland Finnegan's 39-yard interception return for a touchdown.  San Francisco tried to make a comeback as Smith found Hill again on a 3-yard touchdown pass, yet Tennessee's defense held up for the victory.
Question: How many times did the lead change in the fourth?
Answer: 2