ALLEN PARK — Coach Jim Schwartz said today that he won’t announce the starting quarterback for Sunday’s game against Pittsburgh until Sunday.

Rookie Matthew Stafford, who has started the first four games, injured his knee in the fourth quarter of the loss at Chicago. He was limited in practice today. It was his first participation in practice all week.

“There’s a lot of time between now and Sunday. I think (Stafford’s) arrow is trending up,’’ Schwartz said after practice.

Daunte Culpepper has been taking snaps with the starters in practice this week.  When he finished out the game at Chicago it was his first game action of the season. Culpepper said he prepares with the same intensity every week.

“Daunte is a guy who has a lot of experience in the league and he’s a guy who prepares like a starter. He’s always been a starter in the NFL,’’ Schwartz said.
 
— PAULA PASCHE