Tyre life on the red option rubber is a key unknown ahead of IndyCar’s Grand Prix of St Petersburg, according to Will Power.

There have been no longer runs at all on the softer tyres, with just two, 45-minute practice sessions ahead of qualifying, and the latter of those being interrupted by three red flag periods.

Another half an hour of running remains before the 100-lap contest around the St Petersburg streets but Power, who qualified second, thinks even that will not be a reliable indication of how the race will play out.

“No one’s done more than two laps on them; well, you know, we heat cycled them and did another one or two laps,” noted the Team Penske driver.

“That’ll be an interesting story tomorrow, because I don’t even think in Warm Up you’ll be able to tell because the conditions will be so cool and good.

“You won’t get a feel for if they’re going to go off or not.”

Romain Grosjean, who is set to start fifth in his Andretti Autosport entry, had a similar view.

“We’re pretty good on the blacks,” said the Frenchman.

“As everyone said, the reds are going to be quite interesting tomorrow, so it’s going to be most of the time on the blacks.

“We’ve got a we’ve got a good car. Which [compound] to start on? Ah, yeah, that’s going to be a question after the Warm Up.”

The Warm Up takes place tomorrow morning at 0:45 AEDT before race start at 04:25 AEDT, with live streaming on Stan Sport from 04:00 AEDT.