Jaime Alguersuari admits his seventh-place finish in Korea was rather unexpected as he didn't think he would be able to overtake Nico Rosberg.
The Spanish driver, who started 11th on the grid, found himself P8 after his final pit stop but he put his foot down to keep Rosberg on his toes. He finally got his break on the final lap when the Mercedes GP driver's old tyres gave way and he made the most of the opportunity to pass him.
Alguersuari feels the team deserve the P7, which equals his best finish in F1, as they have improved a lot in the last two races.
"The reality is that the Toro Rosso team has done a fantastic job, not just this weekend, but also going back to Suzuka, where we introduced some updates on the car," said the Spaniard. "In Japan, we did not make the most of them but in the few days in between the races the team has done really well to move forward for here.
"The car had fantastic straight line speed which is how I managed to pass Nico on the final lap. I must say I did not think I could do it, I did not expect it, but I gave it one last effort at the end I was able to get past, partly helped by the fact he made a small mistake on that lap.
"Combined with great pit stops, that is how we managed to produce this fantastic result. I am very happy for the team who have worked so hard, especially the mechanics fitting all these new parts."
Alguersuari's six points combined with his team-mate Sebastien Buemi's two mean Toro Rosso are now breathing down Sauber's neck in the Constructors' Championship. The Faenza squad have 37 points compared to the seventh-placed Sauber's 40.
"We are closer to Sauber now and with three races remaining, I think we have a chance of passing them, as long as we continue to perform like this, finishing in the top ten," he said.