Coming off their home win over the Browns, the Ravens flew to Heinz Field for their first road game of the year, as they played a Week 4 MNF duel with the throwback-clad Pittsburgh Steelers.  In the first quarter, Baltimore trailed early as Steelers kicker Jeff Reed got a 49-yard field goal.  The Ravens responded with kicker Matt Stover getting a 33-yard field goal.  Baltimore gained the lead in the second quarter as Stover kicked a 20-yard field goal, while rookie quarterback Joe Flacco completed his first career touchdown pass as he hooked up with TE Daniel Wilcox from 4 yards out. In the third quarter, Pittsburgh took the lead with quarterback Ben Roethlisberger completing a 38-yard TD pass to WR Santonio Holmes, along with LB James Harrison forcing a fumble from Flacco with LB LaMarr Woodley returning the fumble 7 yards for a touchdown.  In the fourth quarter, the Steelers increased their lead with Reed getting a 19-yard field goal.  Afterwards, the Ravens tied the game with RB Le'Ron McClain getting a 2-yard TD run.  However, despite winning the coin toss in overtime, Baltimore was unable to gain ground.  In the end, Pittsburgh sealed Baltimore's fate as Reed nailed the game-winning 46-yard field goal.
Question: Which quarterback fumbled the ball?
Answer: Joe Flacco