The Boston Celtics are in danger of playing without their starting center, Al Horford, when they take on the Chicago Bulls on Monday. He revealed after their game on Sunday that his knee hurts, and that he is uncertain if he can see action the next day.

The Celtics' four-time All-Star then said that it will depend on how he feels in the morning, and his status may be determined closer to tip-off.

This is the first time this season that Al Horford could miss a game due to his knee. Although he wasn't able to appear in two matches last month, it was because of a concussion. His potential absence will be make the Celtics thin upfront, and his ability to stretch the floor and make plays for his teammates will surely be missed.

Horford is enjoying a solid season so far for the Celtics, averaging 13.8 points, including 43.9 percent from 3-point distance, to go along with 8.1 rebounds, 5.3 assists, and 1.0 block through 25 games. His percentage from beyond the arc is a career-high, and the team has continued to benefit from his outside shooting.

Aron Baynes is expected to see an uptick in his playing time, and could take Horford's place in the starting lineup if he is given the night off on Monday. Daniel Theis and Jayson Tatum may receive additional minutes as well, depending on matchups.