By virtue of winning Defensive Player of the Year.
Smart would have been an unrestricted free agent after running down the 4-year $51.5m contract he signed in 2018. He would have been eligible for a full 5-year supermax contract worth $253.88m, starting at $43.27m for the 22/23 season and paying him $58.88m in his final year.
The Celtics and Brad Stevens instead signed Smart to a 4-year $77 million extension in the 2021 off-season.
If Smart had turned down the extension in 2021 and instead become a free agent, what would the Celtics have had to pay to retain him? What offers would have have gotten on the open market?