Tim Duncan, who declared himself "a Spur for life" in March, reportedly has followed through on his intentions to remain in San Antonio.

The 36-year-old franchise cornerstone has agreed to a three-year contract to return to the Spurs, Yahoo! Sports reported Tuesday. The website reported the contract is expected to be worth approximately $36 million, or in the same range of the deal that Kevin Garnett agreed to with the Boston Celtics last week.

Yahoo Sports! reports Duncan's deal is fully guaranteed and the third year of the contract is a player's option. The deal also includes a no-trade clause, the website reported.

Duncan, a two-time MVP, averaged 15.4 points and 9.0 rebounds last season. The 15-year veteran, selected No. 1 overall by the Spurs in 1997, has career averages of 20.3 points and 11.3 rebounds in 1,111 games and has helped the Spurs win four NBA championships.

The Spurs also have agreed to deals with two of their key role players from last season, when San Antonio won an NBA-best 50 games.

Guard Danny Green, a restricted free agent, agreed to a three-year, $11.3 million contract (fully guaranteed), a source familiar with the negotiations told ESPNNewYork.com's Ian Begley, and forward Boris Diaw, an unrestricted free agent, agreed to a two-year, $9 million deal to return to San Antonio, a source confirmed to ESPN The Magazine's Ric Bucher.

Diaw's contract includes incentives that could push the total value to $9.2 million and includes a player option for the 2013-14 season.

Yahoo! Sports earlier reported the terms of the agreements.

Green, 25, started 38 games last season. In 66 games, he averaged 9.1 points and hit 43 percent of his 3-point attempts.

Diaw, 30, who signed with the Spurs after being waived by the Charlotte Bobcats in March, averaged 4.7 points and 4.2 rebounds in 20 games with San Antonio.