Williams driver George Russell has said the "horrific" hard tyre could force drivers into a two stop race on Sunday purely to avoid having to run the compound.
After running compounds one step softer than normal at the 70th Anniversary Grand Prix last week, Pirelli brought the hardest compounds in its catalogue to Spain.
Normally run in May, the postponed grand prix will be competed in considerably warmer temperatures than normal and, given the abrasive track surface, the decision on compounds seemed a sensible one.
But the drivers disagree, with George Russell not holding back on his criticism.
The Williams driver said: "It was horrific. It’s going to be weird because ordinarily, if you want to make a one stop work you’d say medium-hard, but the hard was so rubbish I think it’s a better tyre to go onto the soft tyre.
“So probably a two stop. Soft-medium-medium, or soft-medium-soft is going to be better than putting that hard on because it deserves no place on a Formula 1 car.”
Russell had sat out the first practice session of the weekend to allow Williams development driver Roy Nissany some seat time, but heading out on hard tyres at the start of practice two is a move the Briton feels "didn't help" his session.
Russell added: "I started on the hard tyre which everybody was struggling a huge amount [on], so having a missed P1 and then going straight in on the harder tyre didn’t help.
“Then just struggling to get the tyre working. We’re not used to seeing Barcelona in these track conditions. We pre-empted that but probably we need to go a little step further."
The Williams driver was not alone in his criticism of the hard Pirelli rubber.
McLaren driver Lando Norris branded the compound as "Garbage".
He said: "I feel like I would have more grip on the wets than the hards. I don’t know why.
“I think it’s similar for everyone. Anytime anyone was on the hard tyre they looked awful, then they went on the medium or the soft and improved massively."
Looking for a brighter side to the situation, Norris added: "That’s the way it is and I think we have to understand what we want to do for our plan tomorrow and our use for the race, but it should make it a little bit more exciting.”
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