Celtics legend Paul Pierce was traded to the Nets in 2013, but longtime team equipment manager John Connor always figured he would return at some point. So Connor kept one pair of Pierce’s size-15 custom Nikes at TD Garden, and another at the team’s Waltham training facility, just in case.

On Monday, Pierce returned to Boston to sign a contract with the Celtics, allowing him to retire as a member of the organization. After signing the contract, Pierce went down to the team’s practice court, where Connor finally had some use for those old Nikes.

Pierce put on the shoes and Celtics warm-up gear and fired up some jump shots, and for a moment for the team executives and staffers in attendance, it was as if he had never left. When the session was complete, Pierce signed the shoes, gave them back to Connor, and told him to raffle them off for a team charity.

It had been known for some time that Pierce planned to retire as a Celtic. And while this was certainly a feel-good photo opportunity for the organization, it was also something that was even more meaningful to Pierce, who spent his first 15 pro seasons in Boston.

“Paul and his agent [Jeff Schwartz], ever since the Clippers released him, were very eager to have him back in green one more time,’’ Celtics assistant general manager Mike Zarren said. “This was a strong request of his to do it, and we were really happy to do it.’’

The Celtics selected Pierce with the 10th pick of the 1998 draft. He was a 10-time All-Star and he helped guide the Celtics to the 2008 NBA title.

“It’s an honor to have this opportunity to once again call myself a Boston Celtic,’’ Pierce said in a statement released by the team. “The organization and city took me in and made me one of their own, and I couldn’t imagine ending my career any other way. I’m a Celtic for life.’’

Pierce averaged 21.8 points, 6 rebounds, and 3.9 assists per game during his 15 seasons with the Celtics. He is the franchise’s all-time leaders in 3-pointers, free throws, and steals, and is second on the all-time scoring list, trailing only John Havlicek.

“He is among the very best Celtics, a champion on and off the court,’’ co-owner Wyc Grousbeck said. “We congratulate Paul on a Hall of Fame career, and look forward to seeing his number raised to the rafters of TD Garden.’’

Pierce in February played his final game at TD Garden, when the Clippers visited the Celtics. He started the game and played the first five minutes, and then re-entered in the final seconds and drilled a 3-pointer. His No. 34 is expected to be retired next season.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach