Duke’s season may have taken a turn for the worse.

The Blue Devils’ lost their most important player Monday night, indefinitely, and with it their invincibility. Tre Jones, the least heralded of the Fab Four, is the floor leader of their top-ranked team as the head of Duke’s offense and defense.

Jones dove for a loose ball and landed on his right shoulder five minutes into the game against Syracuse and left the court holding his right hand to his waist. X-rays were negative, but a sprained shoulder can take anywhere from two to six weeks to heal. Mike Krzyzewski said “life happened to our team tonight.”

Playing the rest of the game without Jones and flu-stricken fellow freshman Cam Reddish, who hit the buzzer-beater at Florida State Saturday, the Blue Devils suffered their first ACC loss to the Orange, which needed a big win after going down at home to surprising Georgia Tech in their last game.

Coach K wasn’t sure but guessed Jones “will be out for a while,” and the timing could not be worse with fourth-ranked Virginia coming to Cameron Indoor Saturday afternoon. Reddish, who got sick just before the start of the Syracuse game, will likely be back, but Jones is the engine that makes Duke go.

He is as pure of a point guard as you will find, a selfless floor general who makes the pass first and can make the shot if he is open. He averages eight points, just under six assists and only one turnover per game. But he is equally important on the other end, applying on-the-ball pressure in what has become Duke’s best man-to-man defense in years. He forces the dribbler to turn to avoid getting stripped, allowing teammates to cut off the passing lanes.

Jones’ absence may make scoring stars Zion Williamson and R.J. Barrett handle the ball more under increased defensive pressure from opponents. Jones’ brother, Tyus, from the 2015 national championship team, set up Jahlil Okafor and Justise Winslow. The younger version already looks as good and as important. Duke will be a different team until he returns.