Crennel has said throughout training camp that the backup spot is up for grabs and this could be Stanzi's best opportunity to beat out Brady Quinn.
Quinn was the first off the bench last Friday in the preseason opener. Both have swapped spots throughout camp, but it is the more-experienced Quinn who is considered the favorite.
"We talked about evaluating quarterbacks, and this gives [Stanzi] a chance to be the second guy in and see what he can do," Crennel said. "They're both working hard, they both understand the offense, they both have command in the huddle, and it's still close.
"I can't make a decision yet. ... one guy's had game experience with the second unit, and now we're going to give the next guy experience with the second unit and see what we can do."
Quinn's performance against Arizona left room for evaluation; he completed 7 of 13 passes for 81 yards. He was off target on several throws and also had an interception.
Stanzi, the team's fifth-round pick in 2011, led the Chiefs to two scoring drives against Arizona but benefitted from short fields. He was 2 of 7 for 42 yards.
Crennel said that he's not sure whether Quinn will play against St. Louis because he has not decided how deep Matt Cassel will go in the game.
It's unknown whether Flowers will be ready for the Sept. 9 regular-season opener against Atlanta but doubt grows by the day.
"Everybody heals differently, so all we can do is talk to our trainer who consults with the doctors and try to find out what they know, what they think, and then they let me know," Crennel said. "It's always when he's ready. I don't know his body, he knows his body better than I do. He knows whether he's hurt or what he's capable of."
Pass rush improved: The Chiefs have not had two players finish with double-digit sacks since Neil Smith and Derrick Thomas in 1994. The hope is that streak will end this season with the combination of outside linebackers Tambi Hali and Justin Houston. Hali has 26 1/2 sacks the last two seasons and Houston, who had a sack against Arizona, racked up all 5 1/2 of his sacks in the final five games of his rookie season.
"With all of the guys that we have acquired, we will be able to generate more pass rushing on the teams we are going to play this year," Hali told the Kansas City Star. "Not just from my standpoint, but from all over the defense, from the outside linebackers to the safeties, I think we are all getting ready for the pass rush, and that's a good thing."