The 28-year-old forward is reportedly receiving "strong interest" from Nike, New Balance, and Chinese brand Anta, according to ESPN's Nick DePaula.
It was during Hayward's second season with the Utah Jazz in 2011-12 when he inked a deal with Chinese brand Peak. He's recently been under contract with Nike, with his deal expiring this month.
New Balance partnered with the Celtics organization to create their new 70,000-square-foot practice facility at Boston Landing called the Auerbach Center.
Hayward suffered a catastrophic leg injury during Boston's 2017-18 season opener against the Cleveland Cavaliers, months after signing a four-year max contract with the organization. He averaged 21.9 points, 5.4 rebounds, and 3.5 assists the year prior in Salt Lake City.