Allen suffered the injury at the conclusion of Tuesday evening's practice as he drove to the basket and landed awkwardly on his left foot. He is scheduled to have surgery on Thursday, which will be performed by Dr. Craig Bennett at Kernan Hospital in Baltimore.
"We are devastated for Seth," said Turgeon. "He was playing at a very high level throughout the summer and fall and was poised to have an excellent start to the season. We will support Seth during his rehabilitation process and will prepare him, so he can get back on the court with his teammates."
In 36 career games (seven starts), Allen has averaged 7.8 points and 2.3 assists per game.