Paul Pierce
On June 28, 2007, the Sonics traded Allen and Glen Davis, the 35th overall pick in the 2007 NBA draft, to the Celtics in exchange for Delonte West, Wally Szczerbiak, and the fifth overall pick, Jeff Green. Shortly after acquiring Allen, the Celtics acquired Minnesota Timberwolves forward Kevin Garnett to play alongside Allen and Paul Pierce. Upon joining the Celtics, Allen changed his jersey to number 20 because Paul Pierce already had number 34 in Boston.