The 6-foot-5 Allen had a disappointing campaign both on and off the court. He battled numerous injuries, was suspended for a game due to a tripping incident -- and also saw his NBA stock take a hit.
Allen averaged 14.5 points, 3.7 rebounds and 3.5 assists per game this past season. Had he left Duke after his sophomore year, during which he averaged 21.6 points, Allen would have likely been selected in the first round of the 2016 NBA draft, according to multiple NBA executives.
Those same NBA executives said that Allen would likely be taken somewhere in the second round if he opted to leave Duke now.
"The last few weeks have provided the opportunity for a lot of reflection and prayer," Allen said in a statement released by the school. "I'm a firm believer that when something feels right, you go with it. The chance to play with next year's team just felt right."
The Blue Devils will lose Jayson Tatum, Luke Kennard and Harry Giles to the NBA -- and seniors Amile Jefferson and Matt Jones. However, coach Mike Krzyzewski will bring in another stellar recruiting class -- and will return Allen. It's still unclear whether freshman guard Frank Jackson will return, but Marques Bolden is expected to remain in Durham for his sophomore season.
Duke has two top recruits already committed for the 2017-18 season in big man Wendell Carter (No. 4 in the ESPN 100) and wing Gary Trent Jr. (No. 7), and remains in the mix for point guard Trevon Duval (No. 5) and forward Kevin Knox (No. 9).