Toro Rosso team principal Franz Tost believes that duo Carlos Sainz Jr. and Daniil Kvyat underperformed at the Monaco Grand Prix.
At Sunday's race, Kvyat retired after colliding with Renault driver Kevin Magnussen while Sainz Jr. crossed the chequered flag in eighth position.
Tost believes that their Ferrari-powered engine should have been able to finish within the top-five of Sunday's grid.
Suffering two faulty pitstops, Force India driver Sergio Perez, who ended up on the podium, managed to pip the Spaniard in the pit lane on one of the pitstops, something which Tost laments.
"It's very disappointing to finish Carlos’ race only in P8, when we know we have a package which has the performance to be at least within the top five," the 60-year-old claimed.
"The main reason for this result was the first pit-stop, during which we lost two seconds and where Perez, Vettel and Hulkenberg passed us.
"Therefore, Carlos ended up behind this train of cars and couldn’t use all the potential of the car, but he did a solid race and showed a really good performance.
"On Daniil's car we had a problem with the software during the Safety Car period at the start of the race, where he was stuck in pit-limiter mode, driving at only 60kph. Although we changed the steering wheel, this didn’t help and he therefore was a lap down when the race was restarted. He then had a collision with another driver and did not finish the race.
"We all expected much more from this event in Monaco and we have to be more concentrated in order to prevent mistakes in the upcoming races."