The Spaniard an impressive sixth, immediately behind the two Red Bull cars of Max Verstappen and Daniel Ricciardo, after the Italian team backed up its strong Thursday performance when it mattered.

Sainz had qualified down in 12th position in the previous race in Spain, over two seconds off the pace, but finished less than a second off pole in Monte Carlo.

He was particularly pleased that Toro Rosso was able to respond after other midfield teams showed well early in qualifying and admitted the result was a surprise and a boost for the team.

"It's a good surprise for all of us, because it has been a tricky first five races," he said. "I think we all expected a bit more from the car and the pace, and suddenly to get this P6 in Monaco is the best boost for everyone."

He added: "We put the same car on track that we had in Barcelona. We obviously had to adapt the set-up for this kind of track, and all of a sudden we see ourselves P4. The analysis has to be done.

"Probably there are not a lot of straights here, and this is helping us. Second, I think we have a good car in terms of mechanical grip, which is something maybe last year we were not as good. As I've said on many occasions, the car is more complete."

Sainz insisted he will not hold back at the start of the race despite having the sister Red Bull cars in front of him.

"I always attack. I don't know what Helmut Marko will tell me," joked Sainz. "But I always want to attack from the beginning, because to go into a race defending, is I think the worst thing you can do to your approach and your self-esteem.

"So I'm going to attack at the start, and then I'm going to be patient. It's a long race, more than 70 laps, you just need to be quite lucky with the safety cars, with the timing."