The Eagles and Cincinnati Bengals played to a 13-13 tie.  Donovan McNabb turned the ball over on a sack at the end of the first quarter, leading to a Bengal field goal.  A 44-yard catch and run by Correll Buckhalter set up a 42-yard David Akers field goal to tie the score early in the second quarter.  McNabb was picked off in Bengal territory with less than two minutes left in the half, and Cincinnati scored four plays later on a 26-yard touchdown reception by T. J. Houshmandzadeh.  The Bengals added another field goal early in the third quarter to take a 13-3 lead.  Hank Baskett came up with a 57-yard completion, followed by a 4-yard touchdown reception by L.J. Smith to make it 13-10.  In the fourth quarter, Philadelphia tied the game on a field goal after a 13-play drive.  The offenses struggled throughout the rest of regulation and the game went to overtime.  The Eagles won the toss, but the Bengals had the field position advantage throughout most of overtime.  Nevertheless, neither team could score.  The Bengals had a chance to win on 47-yard field goal attempt by Shayne Graham, but the kick went wide right and the game ended in a tie.  McNabb passed for 338 yards and a touchdown, but had three interceptions (all in Cincinnati territory) and a lost fumble.  The defense registered eight sacks.  This was the first game in the NFL to end in a tie since the 2002 Falcons-Steelers game. It was also played 11 years to the day since the Eagles' last tie game.  After the game, several Philadelphia players, including Donovan McNabb, explained that they did not realize a game could end in a tie, causing controversy because this could have changed the strategy in the overtime period.  (This was a regular season game, so there was a limit of one overtime period.) With the tie, the Eagles fell to 5-4-1, putting them back into last place in the NFC East.
Question: How many times did Donovan McNabb turn the ball over?
Answer: 4