Suns general manager Ryan McDonough was part of the Boston Celtics front office when Boston picked Sullinger 21st overall in 2012.
Sullinger signed a one-year, $6 million deal with Toronto in the offseason after spending his first four seasons with the Celtics.
Sullinger had a screw inserted into the fifth metatarsal in his left foot in October. He was injured in the preseason opener against the Golden State Warriors.
He made his season debut for the Raptors on Jan. 18 and is averaging 3.4 points and 2.5 rebounds in 11 games this year.
Tucker is averaging 7.0 points and 6.0 rebounds in 57 games (17 starts) for the Suns this season.
The deal happened in the last 10 minutes before the trade deadline. McDonough wanted a first-round pick, but then pushed for two second-round picks and got them late. The Atlanta Hawks and Los Angeles Clippers were also interested in Tucker.
Sullinger's trade was first reported by The Vertical.