Pierre Gasly is at a loss to understand why Toro Rosso endured such a difficult time in Singapore, a venue where the Faenza-based outfit believed it would perform well.
Qualifying left both Brendon Hartley and Gasly stranded, respectively in Q1 and Q2, while the race itself was an equally frustrating affair with both drivers finishing well down the order.
"We need to take more time to have a look, because it’s difficult to understand why we were that much slower," said Gasly who concluded his Sunday in Singapore P13.
"The last two weekends were much better than we thought and we thought we had good odds for this weekend in Singapore.
"Finally, we were much slower than expected, so we need to review everything to understand a bit more.
"We saw in qualifying, with windier conditions, I had a loss of downforce in the corners, so there are many things we need to understand, because at the moment we don’t really have all the answers."
Toro Rosso went against the midfield grain and opted to start both its driver on Pirelli's softest compound, the hypersoft, in a bid to instill some strength into their race at the outset.
While the Frenchman took advantage of his rubber early on, his performance just faded thereafter.
"We kind of gambled with the hypersoft in the first stint, but there was a lot more degradation than what we expected," he added.
"After 15 laps I started to struggle massively. We went up to 25 laps, but it was really tough in the end.
"Then with the ultrasofts we got involved in all the mess with Sirotkin, blue flags and everything, so we lost about 15 to 20 seconds.
"That really compromised our race, but I think that even without it, we didn’t have the pace all weekend to fight in the top 10."
For Hartley, who finished a lowly 17th in Singapore, only updates to its STR13 will improve Toro Rosso's track record in the final stretch of the season.
"I think we definitely need some upgrades," said the Kiwi.
"There have been times when we can fight a bit closer to the top 10 – but [Sunday] wasn’t one of them."