When the Boston Celtics traded down from the No. 1 pick in the 2017 NBA Draft, president of basketball operations Danny Ainge revealed that the team would still likely take the player that they would have taken with the first pick.That player, of course, turned out to be Jayson Tatum out of Duke University.After an impressive Summer League, Tatum has continued his strong impression into the preseason and is slated to receive a lot of minutes for the Celtics, potentially even starting at power forward right out of the gates.While Tatum’s knack of scoring led to some analysts calling him one of the most NBA-ready players in the 2017 draft class, it is his work on the defensive side of the ball that has caught the attention of his head coach Brad Stevens, who admitted that he was caught off guard at how advanced the No. 3 pick is."I don't know if surprised is the right word, but Jayson Tatum's defense is beyond his years," Stevens told reporters on Monday, per Jay King of MassLive.com. "He's very savvy and very long. He uses his length. His arms are out and he gets his hands on balls and deflects passes and discourages drives just because of his length. I think he'll continue to get better and better with the other stuff systemically, but he's done a good job for a young guy so far.”

Interestingly, Stevens didn't originally key in on Tatum’s defensive skills when reviewing tape on him and watching him play in person before the draft. Instead, Ainge was the one who liked him for his defensive versatility.

"I've always erred on the side of watching guys play of watching what they can do offensively because I think there will always be the opportunity to figure out your best method to guard with your group,” the coach said. “I probably spent more time watching him on the other end of the court.”

"I didn't watch him nearly as much as Danny (Ainge) and his group (during the pre-draft process), but the length was a major factor and one of the reasons why we liked him," Stevens noted. "It's proven to be a real asset on the defensive end.”

Due to Tatum’s athletic 6’9” frame, he could presumably guard the shooting guard, small forward and power forward positions if called upon. Against teams who will likely employ small-ball lineups like the Golden State Warriors or Cleveland Cavaliers, he could even match up against whoever lines up at center (in this example Draymond Green or Kevin Love).

While he might not be asked to score 20 points per game during his rookie year, Tatum’s ability to defend at a high level could certainly allow him to average somewhere around 30 minutes per game for Boston. As of right now, he’s certainly in Coach Stevens’ good graces.