The Boston Celtics stepped up their run to the play-offs on Tuesday by upsetting Miami 115-107 for their second victory over the Heat in 10 days. Kevin Garnett recorded 24 points and nine rebounds and Rajon Rondo had 18 points and 15 assists for the Celtics (33-24), who are two games out of third spot in the Eastern Conference. Boston have reached the NBA Finals in two of the last four seasons but with an aging roster, few considered them a legitimate title contender until their recent run. \"We\'ve been put to the back burner all year long, this is our opportunity to show the world we still have a lot left in the tank,\" forward Paul Pierce told reporters after scoring a team-high 27 points.