Pedro de la Rosa says he was "shocked and sad" to hear that he had been fired by the Sauber team earlier this year.
The Spanish driver was replaced by Nick Heidfeld for the last five races of the season, as the German returned to the Swiss squad he drove for last year. De la Rosa, who is now Pirelli's official development driver, admitted he saw no indication that he would lose his drive.
"To be honest, I was shocked," de la Rosa told AUTOSPORT. "I had no indication that they would replace me. It was quite a sad decision from the team – from Peter [Sauber], basically.
"I was deeply surprised because there were five races to go, we were all pushing hard and we had a new aero package for Singapore. We had worked very hard to get there. OK, Monza was bad, but we knew that this type of low-downforce track would be always bad for us.
"The car had been a lot better in the last two or three races and we knew that we could do it. From my side it was a strange decision, but life goes on and I'll move on."
De la Rosa, returning to Formula 1 racing full-time for the first time since 2002, said he had no regrets about his decision to join Sauber.
"I came back and I did a solid job. I met some really good people with another approach, another way of working," he added. "Generally, I would do it tomorrow again – it was a very good experience.
"How it ended was not right, especially with five races to go; but, on the other hand, I had an interesting time and I did not stop learning. I can only say thank you for the opportunity, even if we should have stayed together pushing until the end of the season."