Hayward enters NBA's concussion protocol

Boston Celtics star Gordon Hayward has entered the NBA's concussion protocol and is listed as doubtful for Monday's game against the Denver Nuggets, the team announced on Sunday.

The 28-year-old left Saturday's contest against the Atlanta Hawks after making contact with John Collins on a screen.

Hayward has had an up-and-down second season with the Celtics, averaging 10.8 points, 4.3 boards, and 3.4 assists. He missed all but one game last year after suffering a fractured tibia and dislocated ankle in the season opener.