Forget Talladega. Forget Martinsville.

The real wild card in the Chase for the NASCAR Sprint Cup will come in the next-to-last race at the newly paved, newly reconfigured Phoenix International Raceway.

As Carl Edwards said, "It could shake everything up."

Sprint Cup teams spent Tuesday and Wednesday testing on the one-mile track and its new ice-smooth surface after changes that added banking up to a 12-degree tilt have made years of notes obsolete.

The difference could mean five-time defending Sprint Cup champion Jimmie Johnson, who dominated on the old surface with four wins and an average finish of 4.8 in 16 starts, may not be so dominant. It could give the nod to another Chase driver who traditionally has struggled there.

Despite all the testing, we just won't know everything there is to know -- from how many grooves will open up to how cars will react going two-wide in places they couldn't before -- until there's actual competition.

Sprint Cup Series director John Darby described it best.

"I liken it a lot to being able to go through my front door at night in pitch darkness and be able to walk through my living room, negotiate my way into the kitchen, find the light switch without any interference until the night that I come home that it's dark and my wife has rearranged the furniture in the living room and I trip and fall halfway through," he said. "It's the same thing."

In other words, a driver could trip going through the new dogleg at speeds expected to be 2-3 mph faster than the old configuration and throw the whole Chase into a frenzy.

We just won't know.

"Whenever you introduce something new like this new surface and new track layout there are going to be guys that figure it out quickly and guys that struggle," Edwards said during Wednesday's test session. "And it's not necessarily the guys you suspect.

"This race, we're all going to come here with a little nervousness, trepidation. … The way this new surface is, it's unforgiving, so there could be accidents and things that happen we don't usually see at Phoenix."

There are all sorts of unknowns. Will a second groove rubber in as NASCAR hopes to create with vehicles on the track between now and the November race? And what happens on a double-file restart? How will aero issues come into play? How will the hard tires being used to protect against overheating and extensive wear often seen on new surfaces impact strategy on the final call?

"I don't think you can really predict how racing is going to be," said Edwards, tied with Kevin Harvick for the points lead heading into Sunday's race at Kansas. "It's truly unpredictable."

Jeff Gordon said it was "edgy" on his initial trips around the new surface. Although it got better, he acknowledged there are new challenges that everybody will have to deal with in November that can't be worked out in a test.

"That's the thing, when we come here to these tests, we're all trying to learn things, get laps, do our own thing," Gordon said. "We're not racing. We're not getting side-by-side with other cars."

There may be more risks at PIR than there are at Talladega where the so-called "Big One" can happen at any moment, more than at Martinsville where the tight confines on the half-mile track often create havoc.

If the Chase remains as tight as it is now -- nine drivers separated by 19 points -- it likely won't be after Phoenix.

"There are opportunities here for problems that we haven't seen at this racetrack," Edwards said. "I don't know how all of these problems will work out. Double-file restarts with 20 [laps] to go, the second race from the end of the Chase, no telling what's going to happen.

"That's not necessarily good for the racers, but it's good for the fans. It's going to be a little bit stressful."

Wild cards usually are.

And Phoenix now may be the biggest in the Chase.