Vandoorne, who now race in Formula E and is a Mercedes simulator driver, raced for McLaren the past two seasons, with both Honda and Renault power, but didn’t have a successful time.
He had been tipped to potentially do great things in Formula 1 after performing well in most of the series he had raced in, winning the GP2 championship on the way.
But could not find his feet in Formula 1 with a struggling McLaren team.
Vandoorne said to Dutch broadcaster Ziggo Sport: "It was not always easy. Actually, it was very difficult.
"My motor sport career went almost perfectly up until Formula 1.
"I won almost every championship I took part in.
"The timing at McLaren was probably not the best because the car has not been good for several years. Unfortunately, it was not the best years in my career."
When asked if McLaren’s focus on Alonso affected him at the team and his performance he said:"Yes. Unfortunately, I have never been able to tell 99% of what happened.”