Beyond the disappointment of retiring only minutes into Sunday's Belgian Grand Prix, Carlos Sainz believes there may be something under the surface which is undermining Toro Rosso's form and performance.
The Faenza-base outfit had high hopes of raising its game again this year but the last two races failed to deliver any points, for either Sainz or team mate Daniil Kvyat.
Following Spa, the Italian outfit is now seventh in the constructor's standings, having been passed by McLaren.
While Toro Rosso was expecting to struggle on the power front with its year-old spec Ferrari engine, the STR11 chassis has itself been subject to a loss of form.
"We clearly have limitations on the power unit side but that is something we expected and something we were prepared for," Sainz explained.
"We brought an upgrade to Hockenheim to compensate for the power loads that we are losing but it looks like since Hungary we were not performing as we should be.
"There are some question marks in the air at the moment with the team to see why we are not taking the steps with the performance.
"Hockenheim shouldn't have been such a tough track for us and it was similar to here really. We look at the data and see that we are not performing in the corners that we used to perform.
"The team will investigate and hopefully will come up with a solution."
DRIVER RATINGS: Belgian Grand Prix
Toro Rosso's STR 11 was updated with a new front wing and floor, but obviously for some obscure reason, the changes have not been validated on the race track.
"I am not blaming the package at all. It could be something we cannot see in the data. In the same way that nobody understands Pirelli tyres, it can be very difficult to tell with the aero of a car.
"So I am not going to put a blame on that at all, but it is where we need to look because we have dropped a lot of performance over the last two races."
RACE REPORT: Rosberg wins at Spa as Hamilton recovers to third
Breakfast with ... Otmar Szafnauer
Silbermann says ... Spa too hot
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