Dereck Lively II is entering the NBA draft after spending one season at Duke.

The Blue Devils freshman center announced his departure Tuesday afternoon. He’s the second Duke freshman to declare for the draft, joining Dariq Whitehead — his roommate — after he declared last week.

Lively’s lone season in Durham hardly resembled the trajectory of a first-round pick and top-5 recruit, but he came on strong in the second half of the season and was one of the best defensive players in the country by season’s end.

The 7-1, 230-pounder struggled through his first couple of months. Part of that was because of a strained calf suffered in the preseason that held him out of valuable practice time and the season opener; part of it was also an adjustment period to how much contact he could make without being whistled for a foul.

Lively had more fouls (20) than points (19) in his first seven games. He came alive with 11 points in the ACC-Big Ten Challenge win over Ohio State, but was still averaging 3.7 points and 3.2 rebounds through Duke’s first 16 games.

It was that 17th game, a home win against Pittsburgh, in which Lively first provided the full scope of what he could bring to the table defensively.

The Philadelphia native is a game-changing defensive talent, able to both protect the rim and guard smaller players on the perimeter. Pitt’s guards helped turn coach Jeff Capel’s program around, yet that night in Durham they were unable to create on drives against Lively.

“Everyone looked at me at the start and thought I was just going to shoot up every shot at the start of every possession. That’s never who I was,” Lively said during the NCAA tournament. “That’s not the reason I got to the position where I was in high school.

“The reason I got where I did in high school was playing defense, blocking shots, I was a great teammate.”

Lively’s season-high of eight blocks came in Duke’s home win over North Carolina, in which he also had a season-high 14 rebounds. He scored four points in that game, including the go-ahead put-back dunk that broke a tie late in the game.

All six of his games this season with double-digit rebounds came in Duke’s last 18 games.

Lively will take a raw offensive skillset — he still wound up averaging 5.2 points per game — to the NBA along with elite defensive abilities. He’s the rare highly rated recruit who made a larger impact on the defensive end than the offensive end, and it’s likely going to make him a first-round pick and possibly the first ACC player off the board (if it’s not him, it could be Whitehead).

For Duke, Lively's departure opens a need for coach Jon Scheyer to pursue a rim-protecting center through the transfer portal.