Saunders, who was previously Garnett's head coach with the Minnesota Timberwolves, told Sid Hartman of the Minnesota Star Tribune he is "positive" Garnett will re-up with the Celtics. Hartman did not elaborate on whether Garnett told Saunders that directly of if he is simply basing it on Garnett's behaviors he observed while serving in his role with the Celtics.
Saunders was around the team about as much as he could be, sitting in on just about every team meeting, coach's meeting and player's meeting; so Saunders' opinion is more than that of your casual observer.
Other teams, such as the San Antonio Spurs, have also been reportedly interested in Garnett's services, as reported by Buck Harvey of the San Antonio Express-News, but if Saunders is correct, it seems they are out of the running already.
The re-signing of Garnett is likely the No. 1 priority for the Celtics this offseason, so if he is indeed on board, that would be be one less thing for the team to worry about and would allow them to move on to other possible acquisitions and re-signings.
The Celtics have many other decisions to make with players like Ray Allen, Jeff Green and Brandon Bass—all of whom will be free agents come July.