Tim Duncan could have easily gone out on top, with his fifth NBA championship trophy under his arm and his health intact just a few months after his 38th birthday.There’s just no way. Duncan is having too much fun with his San Antonio Spurs coaches and teammates, and he’s playing too well to call it quits now.Duncan has decided to exercise the option on his contract for 2014-15 and will return next season, a person with knowledge of the decision told The Associated Press on Monday. The person requested anonymity because an official announcement has not been made.As the Spurs beat the two-time defending champion Miami Heat in the NBA Finals earlier this month, Duncan was asked several times about his future, as he has been for the last five or six years.