A concussion knocked Detroit Lions defensive end Cliff Avril out of Sunday's game against the Minnesota Vikings in the third quarter, according to Dave Birkett of the Detroit Free Press. The injury was initially described as a head injury, but further evaluation has caused the team to officially label it a concussion.

On Minnesota's first possession of the second half, Avril was noticeably shaken up before heading to the sideline. The veteran had been dealing with a back injury earlier in the week, but he played fairly well in the first half as the Lions tried to keep up.

Over the first nine weeks of the season, Avril has recorded 20 tackles and 4.5 sacks, putting him slightly below the pace he set while recording 11 sacks last season. If the injury keeps him out for a significant period of time, expect Lawrence Jackson to get the bulk of the reps in his place.

This story originally appeared on SBNation.com.