The Broncos' defense surrendered only three field goals by Texans' placekicker Nick Novak, and spoiled quarterback Brock Osweiler's return to Denver, allowing only 131 passing yards. Osweiler spent the previous four seasons (2012-2015) as Peyton Manning's backup quarterback, and started seven games in 2015 while Manning was injured. The Broncos scored three offensive touchdowns: a 4-yard pass from quarterback Trevor Siemian to Demaryius Thomas, plus two rushing touchdowns, one from C. J. Anderson, and the other from rookie Devontae Booker. Placekicker Brandon McManus also added two field goals. This was the first of two games in which the Broncos wore wear their alternate navy blue uniforms&#8212;the other was Week 15 vs. the New England Patriots. This was Broncos' head coach Gary Kubiak's first victory against the Texans, for whom he coached from 2006-2013, as well as Kubiak's return to the sideline following a health scare that forced him to miss the team's Week 6 loss to the San Diego Chargers. During halftime, three former Broncos were inducted into the Ring of Fame: Placekicker Jason Elam, who played with the Broncos from 1993-2007 and is the franchise's all-time leader in field goals (395) and points scored (1,786); defensive lineman Simon Fletcher, who played with the Broncos from 1985-1995 and is the franchise's all-time leader in sacks (97.5) and consecutive games played (172); safety John Lynch, who played four seasons with the Broncos from 2004-2007.
Question: How many years did Osweiler spend as Peyton Manning's backup quarterback?
Answer: four seasons; 4