Michigan State freshman Jaren Jackson Jr. announced Monday that he will enter the NBA draft.

Jackson -- a 6-foot-11, shot-blocking forward -- is projected by many to be a top-five pick in June. Jackson, who has signed an agent, was named the top freshman and the top overall defender in the Big Ten during his one season at Michigan State.

"This was not an automatic decision," Jackson said in a note to Spartans fans that he shared Monday via social media. "And honestly, thank you for making it one of the toughest decisions I've ever had to think about."

Coach Tom Izzo said in a statement that he was looking forward to Jackson's move to the NBA.

"He was a tremendous talent when he first stepped on campus, but when I think about the way he's improved so much in just one year, especially defensively and with the ball, the sky's the limit on what he can accomplish," Izzo said. "There's no question he could be one of the first few players selected in the draft."

Jackson averaged 10.9 points and 5.8 rebounds per game while part of a deep rotation in Michigan State's frontcourt this season. He set a school record by blocking 106 shots during his freshman campaign.

He said in his note that he plans to finish his studies at Michigan State. He is one of three underclassmen from this year's team who plan to at least explore the NBA as an option in the coming months. Sophomore Miles Bridges announced last week that he hired an agent and planned to go pro. Sophomore Nick Ward also plans to enter his name in the NBA draft but has not hired an agent, which means he could return to East Lansing next season.