Detroit Lions coach Jim Schwartz has eased concerns over the fitness of Reggie Bush after the running back picked up a knee injury during Sunday's loss against the Arizona Cardinals.

Bush initially left the field in the second quarter following a collision with Arizona safety Tony Jeffersen, only to return later in the same period. He left the game for good after a fumble in the third quarter and admitted after the match that he should not have come back to the action at all.

However, Schwartz has played down the injury, saying that he did not think the former second overall draft pick would miss a substantial amount of time.

"The tests today were encouraging. He's going to be sore but he doesn't have anything that is going to be long term," Schwartz told reporters. "It's too hard to speculate on injuries. That's why I usually don't."

Bush joined the Lions this off-season after a two-year spell with the Miami Dolphins.