The Boston Celtics have secured the best player on their team for the long term. On Sunday, they agreed to a five-year, $195 million rookie max extension with young star Jayson Tatum, according to ESPN's Adrian Wojnarowski. The deal, which kicks in after this season, will keep Tatum in Boston until 2026. Or, at least, until 2025. There is a player option for the fifth year, per Wojnarowski. 

After a bit of an up-and-down start to his career, Tatum took the leap last season and established himself as the main man on the Celtics. He really took off in the second half of the season, and was dynamite in the playoffs, where he put up 25.7 points, 10 rebounds and five assists per game on the Celtics' run to the Eastern Conference finals. 

He was always likely to get a max extension, but after a performance like that on the big stage, he essentially had a blank check from Danny Ainge and Co. Tatum now joins Kings guard De'Aaron Fox and Jazz guard Donovan Mitchell as members of the 2017 draft class to ink max rookie extensions this offseason. 

With the departures of Kyrie Irving and Al Horford prior to last season, Tatum was forced to take on a much bigger role, and showed he had no problem handling that kind of responsibility. His efficiency actually jumped along with his usage rate, and he became a deadly 3-point shooter. In particular, his ability to knock down 3s off the dribble on a consistent basis -- 40.4 percent on those attempts -- made him borderline unguardable at times. 

He still has room to improve with his finishing around the basket, where he misses more easy looks than you would like, and we'll have to see if the playmaking he flashed in the playoffs is real. If it is, Tatum will truly be the full package on the offensive end. And now that Gordon Hayward is gone, the Celtics will look to Tatum even more to carry them on that side of the ball.

Jayson Tatum
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Tatum doesn't just contribute on offense, however. He can stake a claim as one of the best two-way players in the league, thanks to his fantastic defensive instincts. With his length and timing, he is an absolute menace in the passing lanes, and he has the size and athleticism to guard multiple positions. It wouldn't be a surprise if he makes an All-Defense appearance before this contract is up. 

An All-Star and All-NBA honoree for the first time last season, Tatum is just beginning his star turn, and the Celtics made the smart move to lock him up as quickly as possible.