Write a question about the following article: The Broncos' defense limited Titans' quarterback Marcus Mariota to only 88 yards passing on 6 of 20 attempts; however, the Titans controlled the first half time of possession by a 2-1 margin and led 10-0 in the first quarter. Running back DeMarco Murray rushed for a 1-yard touchdown and placekicker Ryan Succop kicked a 53-yard field goal; the latter scoring play occurred after the Titans' defense forced a fumble off Broncos' running back Justin Forsett. A 41-yard field goal by Succop just before halftime gave the Titans a 13-0 lead. The Broncos' offense did not cross midfield in the first half. After a scoreless third quarter, the Broncos were attempting to cut into the Titans' lead early in the fourth quarter, but the Titans' defense stopped the Broncos on a 4th-and-goal. After forcing a Titans' punt, the Broncos finally got on the scoreboard with ten minutes remaining in the game, with quarterback Trevor Siemian connecting on a 3-yard touchdown pass to wide receiver Emmanuel Sanders. After forcing a three-and-out from the Titans, the Broncos marched down to as far as the Titans' 16-yard line, but had to settle on a 34-yard field goal by placekicker Brandon McManus to narrow the Titans' lead to 13-10 with 4:33 remaining in the game. After forcing another Titans' punt, the Broncos had one last possession, hoping for a rally. With 1:04 remaining in the game, Siemian completed a pass to tight end A. J. Derby at the 41-yard line, however, Titans' linebacker Avery Williamson forced a fumble off Derby, which was recovered by safety Daimion Stafford to seal the win for the Titans.

Question about the article:
How many passes did Marcus Mariota fail to complete?