The Hawks have not given No. 15 to any player in the two seasons since Horford left.
Carter has worn the number in most of his 20 seasons, including his first 12-plus seasons with the Raptors, Nets and Magic. He switched to No. 25 for a half season after a trade to the Suns (worn by Robin Lopez) and two seasons with the Mavericks. He returned to No. 15 with the Grizzlies, Kings and now Hawks. Carter also wore the number during his collegiate career at North Carolina.
The Hawks acquired Carmelo Anthony as part of a three-team trade this summer with the intention of a buyout for the veteran. Anthony wore No. 15 to start his 15-year career before he switched to No. 7. Although he never was to play for the Hawks, he requested a jersey of the team through social media. The team had a No. 15 Hawks jersey made and presumably sent to Anthony.
Horford had to change to No. 42 with the Celtics. The No. 15 was retired by the franchise so Horford returned to his collegiate number.