Warner hasn't missed a game to injury since 2005, after all.
But when the three-time Super Bowl starter sat out the second half as a precaution Sunday after feeling "fuzzy" from a big hit, the other NFC West teams must have liked what they saw.
This division is the Cardinals' to lose until the minute Warner walks away, probably after next season.
Leinart completed 10 of 14 passes for 74 yards, including a clutch 20-yarder to Early Doucet as Arizona finally handed the Rams their ninth defeat in 10 games. But the Cardinals' offense punted four times and lost a fumble while generating seven first downs and zero points with Leinart at the controls.
Holding Leinart to Warner's standard isn't realistic or fair, but an occasional touchdown might be nice. Leinart has thrown one touchdown pass in his last 127 attempts dating to a 23-20 victory over Seattle early in the 2007 season.
This was the third time Arizona handed over the offense to Leinart this season. The Jaguars, Bears and Rams have outscored Arizona by a 24-0 count with Leinart in the game.
"Am I happy? I'm happy we won," Leinart said. "Obviously, I'm going to get better and keep working and if my opportunity comes, keep making the most of it."
While the Rams pitched a second-half shutout, no one in the Edward Jones Dome played tougher defense than Cardinals coach Ken Whisenhunt. He offered unwavering support for Leinart, but it was a tough sell.
"I think some of it has just been bad luck," Whisenhunt said. "If you go back to Jacksonville, he threw a pass on a naked [bootleg] that was a first down and the guy drops it. He throws a pass today on a naked after just making on that same drive a big third-down conversion to Larry ... and it's fumbled. I mean, that's not Matt's fault."
Leinart overthrew Fitzgerald twice on the Cardinals' first drive of the third quarter. He seemed to hold the ball too long while taking a 9-yard sack on a third-and-3 play with 6:06 remaining in the game. A fumble in that situation could have cost Arizona its second consecutive 7-3 start.
"As with anything, you get into a groove as you are doing it and have some continuity, you get more comfortable," Whisenhunt said. "The play he made to Early, I don't see how you can make a better play than that as a quarterback."
Warner completed 15 of 19 passes for 203 yards, two touchdowns and a 146.3 rating. He had just completed a 14-yard pass to Fitzgerald in the second quarter when Rams safety Oshiomogho Atogwe hit him from behind. Warner appeared shaken, but he stayed in the game for five more plays, leaving only after Beanie Wells' 1-yard touchdown run gave Arizona a 21-3 lead with 2:23 left in the first half.
"It was one of those situations where I didn't feel perfect, so I just wanted to be cautious with it," Warner said. "I actually feel pretty good right now. Just a very, very slight headache. I remember everything that happened. I didn't get knocked out."
Warner said he hasn't suffered a concussion since probably 2003, when he was still with the Rams. The serious injury Anquan Boldin suffered against the Jets last season rattled Warner. Another teammate, Sean Morey, has battled concussions this season. Warner is 38 years old. He has seven children. He made the right decision.
"I think you get farther in your career and you see life beyond football and you realize that this game is just a game," Warner said. "There are other things that you want to do and you want to be smart, especially when it comes to your health. I think that is what I have learned."
Warner overshadowed his former team when he was in the game and through the manner he left it. His St. Louis successor, Marc Bulger, wasn't much of a factor in the outcome -- not a good sign for a player with an $8.5 million salary next season.
But as Leinart showed the Rams on Sunday, drafting a quarterback in the first round assures nothing.
"Not taking anything away from Matt Leinart, because he is capable of getting the job done and they got a ton of weapons still, but I think it just shows you how good Kurt is, that when he comes out, things kind of shut down a little bit more for them," Rams defensive end Chris Long said. "Kurt just makes plays."