Boston, MA -- (Sports Network) - The Boston Celtics signed point guard Rajon Rondo to a multi-year contract extension, the team announced Monday.

Per club policy, terms of the deal were not disclosed. However, the Boston Herald is reporting the deal is for five years, starting with the 2010-11 season, and is worth about $55 million.

"We are extremely pleased to be able to extend Rajon's contract," said Celtics president of basketball operations Danny Ainge. "We believe that he is one of the elite point guards in the NBA and has a tremendous future ahead of him."

Rondo is averaging 6.5 points, 11.8 assists and 5.0 rebounds in four games this season for the unbeaten Celtics. He also has 10 steals.

The 23-year-old product of Kentucky is in his fourth season with the Celtics and has career averages of 9.6 points, 5.8 assists and 4.4 rebounds. He posted career bests last season with 11.9 points, 8.2 assists and 5.2 rebounds in 80 games.

"I would like to thank the Celtics ownership, Danny Ainge, Doc Rivers, my teammates and the Celtics organization for all of their support over the years," said Rondo. "I would also like to thank my family, friends and fans. I'm ready to do everything I can to bring banner 18 to Boston."