Sergio Perez says the decision by McLaren to drop him for next season has come as "a shock", as he was "100%" expecting to stay with the team.
The Mexican, 23, is leaving after only one season with the team, who have chosen to partner novice Kevin Magnussen with Jenson Button for 2014.
"It is a bit of a shock," Perez told BBC Sport.
"[I was going to stay there] 100%. I don't know what happened."
He added: "The contract was signed from my part, I sent it, and then on Friday I had the news [about his departure]."
Perez's Formula 1 career started in 2011 with Sauber, where he secured three podium finishes in two seasons.
Following Lewis Hamilton's decision to leave McLaren for Mercedes, the Woking-based team announced in September 2012 that Perez would join on a multi-year deal from 2013.
Perez has not finished higher than fifth this season, but out-qualified Button on eight occasions and has beaten him in five races.
In total, Perez has picked up 35 points for McLaren, 31 fewer than he accumulated at Sauber in 2012.
Asked whether he felt he had done well at McLaren, Perez said: "I really think so.
"I probably came at the worst possible time to McLaren because the car was very uncompetitive.
"I have half of the points I had at Sauber, but I am driving better this year. It made my adaptation to the team a bit more difficult because the car was so bad this year."
Perez has been linked with a possible move to Force India, while there are also potential vacancies at Lotus and his former team Sauber for next season.
He said: "There are some options out there. I will try to find the best possible one for my future.
"If I don't succeed on that, I am not going to stay in F1 just to stay here and be an F1 driver. I am not bothered at all on that, so maybe I would have to look for something else."