"He's very excited to be with Blake," Brothers said. "And very excited to be with a young upcoming team he believes he can help win a championship."
According to another league source, the Spurs offered Butler a four-year, $21 million deal, the full value of their mid-level exception. The Nets went even bigger -- four years and $30 million, according to sources -- but Butler preferred to play in Los Angeles alongside Griffin and Gordon.
The Clippers had pursued both Butler and Detroit forward Tayshaun Prince this week. The Clippers discussed two- and three-year deals with Prince, according to a league source, but he ultimately elected to re-sign with the Pistons on a four-year, $27 million deal, according to ESPN The Magazine's Ric Bucher.
It was previously reported that the Clippers had only offered Prince a one-year deal, but a source later said that was incorrect.
Butler played just 29 games last season with the Mavs before rupturing the patellar tendon in his right knee on New Year's Day. He underwent major surgery, and despite exhaustive rehab, was unable to return for Dallas' championship run.
Mavs coaches and front office personnel consistently lauded Butler's effort to return and he believes his right knee is back to 100 percent.
Dallas, however, was reluctant to offer Butler anything more than a one-year contract, an approach the club seems to also be taking with its other free agents.
Josh Howard becomes the top swingman on the market now that Butler has agreed with the Clippers. Howard is considering San Antonio, Denver, New Jersey, Utah, Washington and Chicago, sources tell ESPN The Magazine's Chris Broussard.
Ramona Shelburne is a reporter and columnist for ESPNLosAngeles.com. Information from ESPNDallas.com's Jeff Caplan was used in this report.