That left Skelton and newly signed Richard Bartel the only quarterbacks to practice. Bartel had been a third-stringer with Washington and most recently was Daunte Culpepper's backup for Sacramento of the UFL.
Anderson said he has had several concussions and started feeling better on Wednesday.
"But I still haven't passed the quiz," he said.
Whisenhunt said Skelton, a 6-foot-6 fifth-round draft pick out of Fordham, "is making progress."
"He's putting a lot of time in," the coach said. "I'll tell you what, he's here morning, noon and night. The hard part is taking it from the learning aspect and executing it on the field, but he's working hard at it."
Skelton made his NFL debut in the fourth quarter against the Rams, immediately throwing to Steve Breaston for a first down on third-and-15. It was one of only three third-down conversions in 22 tries for Arizona in its past two games.
So if Skelton starts, he won't exactly be directing a juggernaut.
Running back Tim Hightower called Skelton "kind of a laid-back guy."
"It's kind of funny," Hightower said. "He came in the first play and he threw that completion, he kind of just looked at me and shrugged his shoulders. That was his way of calming himself down. I kind of laughed and he laughed and he just moved forward. He wasn't overly excited, he wasn't overly depressed, he was just like `I'm here. Let's do it.' "
Whisenhunt has always resisted playing young players early. But, he said, "We really don't have a lot of choice at this point."
"With Derek's situation, that's when you have a young guy and you prepare that he may have to play at some point," Whisenhunt added.
Whisenhunt said the Cardinals have adjusted their game plan to fit Skelton's strengths. But he would not go so far as to select the rookie out of Fordham as the starter.
"We've still got a whole another day tomorrow to get through with practice and we're still giving them both reps trying to make a determination, as well as see where Derek is."
Whisenhunt said Anderson "definitely still is in the mix."