It was late in the fourth quarter when McCown went down on his back and appeared to injure his finger when Dewayne White cracked him and forced a fumble.
McCown threw for 313 yards and two touchdowns in the opener but also tossed two interceptions and was sacked three times.
The turnovers earned him boos from the Oakland crowd but the touchdowns earned him praise.
While the quarterback controversy seemed to be silenced for a week, it may take on a new level with a division rival the next foe.
And Culpepper was touted as having a great training camp, albeit it short.
"Daunte did a great job," head coach Lane Kiffin said in his postgame press conference after losing to Detroit. "He just didn't have enough time. It was nothing that Daunte didn't do. In practice, I thought Josh was managing things better. Will there come a time when Daunte catches up? There might be."
An injured finger may have nudged Culpepper ahead of McCown in the race.
One thing is certain, don't expect Kiffin to announce the quarterback for this Sunday either.