Jean-Eric Vergne says he is "not bitter" about Red Bull's decision to drop him from the Toro Rosso Formula 1 team in favour of Max Verstappen and Carlos Sainz Jr.
The Frenchman originally lost his Toro Rosso F1 seat to Formula 3 rookie Verstappen in the summer, when Red Bull signed the Dutchman and decided to place him in F1 alongside Daniil Kvyat next year.
But Sebastian Vettel's shock decision to quit Red Bull for Ferrari caused Red Bull to promote Kvyat and created the potential for Vergne to be retained for another season.
But Sainz's title success in Formula Renault 3.5 this year, allied to a strong showing in post-season testing for Red Bull in Abu Dhabi last month, earned the Spaniard promotion to F1 as Verstappen's team-mate, and means Vergne will be without a Red Bull-backed race seat next year.
Vergne, 24, said he accepted the decision to give his seat to Sainz, given Red Bull's history of promoting young drivers, and thanked them for giving him his own chance to race in F1.
"Toro Rosso is a team thanks to Red Bull, with Red Bull money. They are a team that is there for young drivers," Vergne told AUTOSPORT.
"After three years in F1 I'm not a young driver anymore.
"Therefore, it's understandable they [decided] to promote young drivers from their academy, so I'm not bitter about the decision.
"Not so many people are doing this, so it's fantastic for drivers.
"I will always be thankful to Red Bull, because thanks to them I did three years in F1, which gives me many opportunities for the future of my career.
"Of course I was disappointed to lose the race seat, but I showed myself with a really strong performance this season.
"If I would have quit F1 at the end of last year I would have been disappointed, but this year I have nothing to regret and I'm a much better driver."
Vergne said the fact he had endured such a challenging season in 2014 meant he would be much better prepared for the future.
"I know things would have been different if I had less technical problems - the engineers at Toro Rosso say I lost around 50 points to this, plus I couldn't always show [my potential] in qualifying," Vergne added.
"Considering all this, and to keep my head when the decision was taken to put Verstappen in my place, I think I did a strong season.
"I'm too old for Toro Rosso, but still young in F1 with good experience and I will use all of this as motivation to move forward.
"Red Bull has done everything for me; now it's up to me to take the decisions, and I'm really excited about the challenge in front of me.
"With the experience I have, I'm sure I can come up with something really exciting for the future."