Here's the official press release on NBA.com.
Phil Pressey's contract would've become fully guaranteed after today. With the edition of Perry Jones, Boston already has 15 guaranteed contracts for next year (the league maximum), not to mention a deal for Jordan Mickey in the works as well. Jonathan Holmes has also looked good in Summer League, and last night Marcus Thornton The Sequel led the young C's to a rout over the Heat. That's 18 guys potentially in the way of Pressey's roster spot (although Boston does still have over three months to work that out), which forced Danny Ainge's hand.