Task: Question Answering
Input (English): Passage: Coming off their special teams woes in 2010, the Chargers allowed a 103-yard opening kickoff return to Percy Harvin to start the season. Kicker Nate Kaeding suffered a season-ending injury on the play, and punter Mike Scifres assumed place kicking responsibilities for the game. The Chargers outscored the Vikings 10-0 in the fourth quarter to come back and win the game, 24-17. Fullback Mike Tolbert scored three touchdowns, and Philip Rivers completed 33 of 48 passes for 335 yards and two touchdowns. He was also intercepted twice.  Scifres kicked a 40-yard field goal, the first of his NFL career, and kicked three PATs.  With the win, the Chargers started their season out 1-0. 
Question: How many incomplete passes did Philip Rivers throw? 
Answer type: Number 
Output (English): 15.