THERMAL, Calif. The key phrase for this weekends NTT IndyCar race at The Thermal Club is tire deg.

In an effort to create more differentiation from the Firestone Black primary tires and the softer Firestone Red alternate tires, it could have a dramatic impact on Sundays race.

Combine that with much hotter temperatures from last years All-Star Million Dollar Challenge, and a track surface that is very abrasive.

That will make Sundays 65-lap race around the 3.067-mile, 17-turn road course more than a real handful for the 27-driver field.

I think tires are probably the biggest thing, but you need to be fast, said three-time IndyCar Series champion Alex Palou of Chip Ganassi Racing, who easily won here last year. If you are slow and you take care of tires, youre done. If youre fast and you dont take care of tires, youre done as well.

Its a very high deg race or track, at least with what we had last year. And now we have the hybrid on top of that, then we have alternate so I expect that its going to be quite high deg.

Unlike last years exhibition race that did not include pit stops, this years contest will likely feature three, or even four pit stops, depending on how long the soft Firestone Red tires degrade.

Palou believes that adds to the strategic challenge of the race.

Its actually not that bad if we start adding stops, Palou continued. If we do three stops, and then suddenly you can do like, 15 to 20 laps, stints, and you can push, maybe its actually not that much high deg.

But then keeps opens up the door for somebody to do one stop less bank on a yellow and make it work. So, it will be an interesting race.

Palou believes a two-stop race is the goal, and four stops will be too many.

But it could change, he cautioned If the tire deg is huge, we cannot make it in two and maybe four starts to appear if theres yellow.

Marcus Ericsson of Andretti Global believes every driver in the field will make it on three pit stops.

I think on paper, two is possible, but I doubt that the alternates will be able to do that, Ericsson said. If you have really big drop off, three-, or four-second drop off, then a four stop could come into play as well.

If youre a lot slower than someone on track, that extra pit stop goes away quite quickly. That will be another thing thats a bit of an unknown. Maybe someone tries that, are super aggressive, pits out of sequence, whatever you want, that could be a way to do something different.

Sundays race could be a battle of the unknown. Each entry in the race has 10 sets of tires for the weekend, including six sets of Blacks and four sets of Reds.

In the past, drivers believed there wasnt a high degree of different between the two tire compounds. IndyCar and Firestone heard some drivers suggest a bigger gap between the two and this year, they created a bigger difference.

I enjoy it, Ericsson continued. I think the worst part we can have is when everyone knows everything, and its just like everyone has it all figured out before going into the race, and everyone is doing the same tire strategy and pit number and everything. I think thats not fun.

I like this work where its like a bit more unknown, and you have to sort of take decisions on the fly. Also, as a driver, you need to be really good at feeling what the car is doing, what the tires are doing, and communicating that well.

I like that challenge. Thats fun, and it makes also the drivers and teams that does it well.

Alexander Rossi is making his 149th career IndyCar start this weekend at The Thermal Club. He will start his 150th IndyCar race next month in the Acura Grand Prix of Long Beach, where he is a two-time winner.

Rossi believes in the right circumstances, the current difference in tires can spice up the competition.

Listen, its a hard job because I dont envy what theyre having to do in terms of IndyCar has requests to make a bigger differentiation between the primary and the alternate which in principle I dont have any disagreement with, Rossi said. Theyre trying to do it at tracks that we havent had the Hybrid before.

Everyone globally underestimates how much of an impact adding that sort of weight, that sort of torque on corner exiting, regen capabilities under the braking zones, theres a lot of longitudinal demand that wasnt there before, on top of the weight.

In a lot of ways, I think the separation would have come without the tire change. So, what you saw in St. Pete was an alternate that was already fairly fragile in certain scenarios, burdened with extra weight. The result is what you got.

Pato OWard of Arrow McLaren believes the track surface is a cheese grater after Fridays practice.

The common denominator, the deg is going to be big, OWard said. Its like an old Iowa, I would guess.

Kyle Kirkwood was the fastest driver in Fridays practice session as the Andretti Global driver turned a lap at 1:41.8709 for a speed at 108.384 mph in the No. 27 Honda. Teammate Marcus Ericsson was second at 1:42.2314 (108.002 mph) in the No. 28 Honda. Last years Thermal winner, Palou, was third at 1:42.3246 (107.904 mph) in the No. 10 DHL Honda for Chip Ganassi Racing.

Colton Hertas No. 26 Gainbridge Honda for Andretti Global was fourth at 1:42.6078 (107.606 mph) and Team Penskes Scott McLaughlin rounded out the top five at 1:42.6118 (107.603) in the No. 3 Chevrolet.

Rookie Robert Shwartzman of Prema Racing had an issue in practice when a fuel cell issue caused a fire in his No. 83 Chevrolet. The driver from Tel Aviv bailed out of the car, unharmed. However, the car and engine sustained damage and the Prema team was working on repair long after practice concluded.