This weekend's Spanish Grand Prix marks the first appearance of the hard tyre this season, but not long into the opening practice session drivers began abandoning them for the medium version.
"The tyres are already hard enough so the harder compounds are just way too hard," said the Australian. "Hopefully for Barcelona's sake it's hot and therefore these harder tyres work, but if it's cold then it's going to be a struggle for everyone."
While the compounds for races post Austria have yet to be revealed, last year the hards were used at Silverstone, Malaysia, Japan and Brazil.
"If you look at the natural deadline it was before the race in Barcelona, last Thursday," Pirelli's Mario Isola told reporters. "We decided to postpone the choice until after Barcelona, to give to the teams more information on the performance in Barcelona.
"The process is usually that we make a proposal that we agree with the FIA," he added. "Obviously we have to have an internal meeting and decide.
The Italian manufacturer has been the subject of much criticism, with teams and drivers feeling its choice of compounds has been too conservative.
"(In pre-season testing) the supersoft was OK in that condition with those loads," he said. "Now we are with an estimation of the loads of the pre-season test, with a temperature that is different. Some years we have much higher temperatures here, so we have to consider this and that's why I don't have the feeling to say yes, I would go one step softer. We didn't want to oblige the teams to have this compulsory aggressive selection."
Nonetheless, in light of the feedback following Friday's sessions, Pirelli opted to lower the minimum pressure of the rear tyres to 18.5 psi, with the fronts dropping from 22.5 to 22.0 psi. In pre-season testing, Pirelli ran the rears set at 18psi, but this was raised to 20 psi for this weekend to allow for the development of the cars.