That's why it's called practice, though, and why Minnesota Vikings coach Brad Childress isn't in a rush to choose his starting quarterback. Rosenfels shined in the first preseason game, completing 10 of his 13 throws without a turnover and leading the Vikings to 10 points during the two series he played.
"I felt more comfortable out there," Rosenfels said afterward.
Jackson wasn't sharp, but he will have his chance to start this week.
"I've got a lot more work to do," Jackson said.
Just as he's often restrained in expressing public criticism of player performances, Childress was measured in his praise of Rosenfels after the 13-3 victory at Indianapolis from which the Colts held all four of their starting defensive backs out. Childress was also careful to acknowledge that his evaluation of Jackson, who went 7-for-15 for only 39 yards over five possessions, comes in the context of working with mostly backups.
After Sunday's practice, Childress said his film review of the game didn't produce any further revelations about either quarterback, stressing that there's more time left in this competition.
"The numbers are what they are," he said.
Following the game, Childress said he didn't have a timetable for the completion of this process that will largely define the season for the Vikings.
The coach then added this: "I'll know when it's set, though."
Rosenfels was held out of Sunday's practice. Childress said he was doing some running in the pool; Rosenfels hurt his ankle in Friday's game, but he played through it and said he was all right.
Wide receiver Bernard Berrian was also missing from practice. He hurt his hamstring in the game, an injury that Childress downplayed but typically takes at least a few weeks to fully heal.
Given their struggles at the sport's most critical position throughout Childress's time as coach and all of the offseason back and forth with Brett Favre, it seems as if quarterback is the only spot that matters for these Vikings.
That's not quite true, considering center John Sullivan and right tackle Phil Loadholt have never before played a down in an NFL regular season game. Sullivan, playing more than almost all the other starters on Friday, blocked, moved and communicated well.
"Did a good job of just directing the show," Childress said.
Sullivan, who spent his rookie season behind stalwart Matt Birk, was rather uptight on the bus ride to the stadium.
"I did not throw up," he said. "But I was a little nervous. I care about how we play, and about winning. So I think that's just kind of a natural reaction."
He expressed confidence in where his development is currently at. The Vikings host the Kansas City Chiefs on Friday night.
"As much time as I can get right now is good," Sullivan said. "It's the preseason, so obviously everybody knows it doesn't count toward your regular season record, but it's still an important time to build momentum and for me to gain experience."