By ESPNSTAR.com staff
The Woking team eventually finished third, behind Red Bull-Renault and Ferrari, while Button finished the season fifth in the drivers' standings.
However, Button, who won the first Grand Prix of the season in Australia, claimed that he never imagined Red Bull would have emerged victorious after the first five races, instead believing that his McLaren would emerge triumphant after their strong showing.
"After five races I thought we would win the championship," Button was quoted as saying by the Sun.
"We seemed very competitive and at that stage I wouldn't have said Red Bull would win."
Nonetheless, Button still managed to take a credible three victories, with former team-mate Lewis Hamilton winning four over the course of the season, and the 32-year-old expressed his regret that reliability problems would end up foiling their charge for the title despite the team possessing one of the fastest cars.
"You always think you've lost if you haven't won the championship," Button added.
"Red Bull did a very good job and won whereas we still did a good job, just not quite good enough.
"But it's a very competitive sport and we shouldn't be disappointed with how we've gone about our racing."
Button will be joined by Sergio Perez at McLaren in 2013 after Hamilton departed the team for Mercedes.