Carlos Sainz has labelled his “unthinkable” fourth place finish in the Singapore Grand Prix as the best drive of his Formula One career so far.

Despite making a slow start from 10th on the grid after the anti-stall on his Toro Rosso kicked in, Sainz recovered through the order and sealed his career-best result in F1 when Renault’s Nico Hulkenberg was forced into a late retirement.

The Spaniard spent much of the race defending position following a decision to switch onto the super-soft tyre when the track dried up, while the rest of the field opted for Pirelli’s softest available compound, the ultra-soft.

Sainz — who sits ninth in the drivers’ standings on 48 points — has now scored two points more than the total he achieved in 2016, and reckons the race was one of the most important days of his career.

“[It was] the best one, no doubt,” Sainz said. “Apart from the start and with all the complications this race had, I had very good pace on the wet, very good pace on the used inter against the new inter and then managing to fend off guys. So I would say it’s one of the best stints I’ve done in Formula One.

“It was a very important day. One of the most important of my sporting career and I can be very, very happy. It was a result we really earned, doing the right thing every time. There were complicated moments, especially when I had people with new inters behind me and mine were used.

“Then when everybody was on ultras I was on the super-softs and I had to defend very hard from people who were a second quicker than us because of the tyres. Then things started to happen, we passed some people and we finished fourth, which is incredible, unthinkable.”

Although Sainz will spend next season on loan at Renault from Red Bull, there has been speculation in the paddock that he could replace Jolyon Palmer at the French manufacturer as early as the next round at the Malaysian Grand Prix in two weeks’ time.

When asked if he felt drive in Singapore would be a fitting way to bow out of Toro Rosso if it proved to be his last with the team, Sainz replied: “I think so but I’m still not thinking it’s going to be my last race. Since this happened I told my team, my group of engineers, my mechanics, let’s go for this weekend, let’s do a perfect weekend, let’s not worry about what happens next.

“They showed a big amount of support, telling me they were extremely happy for me for my future and altogether we were super motivated and put together a perfect weekend. I am very proud of them and very grateful to them because they’ve been a great source of support.”