Detroit Lions running back Reggie Bush has admitted that he should not have returned to yesterday's match against the Arizona Cardinals having injured his knee.

Bush picked up the injury in a collision with Arizona safety Tony Jefferson during the second quarter, but returned to the match later in that quarter having been cleared by the medical team.

However, the 28-year-old left the game again in the third quarter after fumbling the ball and did not come back this time, acknowledging that he wasn't himself following the injury.

"Yeah, it hurt. I was able to go back in the game, but I wasn't myself," ESPN quotes Bush as saying.

"I probably shouldn't have gone back in. But I went back in and tried to give it a shot. Felt like I could still go, but I wasn't myself.

"We'll see what happens this week, I'm not sure. I don't think it's anything serious."

The Lions went on to lose the match 25-21 following a late fightback from Arizona.