Sebastian Vettel nearly walked away from Formula 1 last year because of the massive changes the sport underwent, claims his former boss Christian Horner.

The four-time champion was reportedly unhappy with the direction the sport took and he was never one to shy away from making his feelings public.

“Seb didn’t enjoy the regulation changes,” Horner told the Guardian. “He didn’t enjoy the new engine, the feel from the new system, the power unit, the brake-by-wire, the lack of downforce.

“You could tell he wasn’t happy. He was preoccupied and to compound that his team-mate won three races. There was that feeling ‘am I enjoying this as much as I thought I was?'”

The German was outclassed by his younger team-mate last year which led to him making the decision to leave Red Bull and join Ferrari.

But that move nearly didn’t happen according to Horner, who says a mid-season change of mind persuaded Vettel to continue in F1.

“It was like someone had taken his toy away. It took him a while to get to grips with that. It was not something he was used to. He went through a period of disillusionment about the direction F1 was going in.

“There was a stage last year when he thought whether he wanted to stop or not, whether he was getting the same level of enjoyment or not and whether or not he wanted to continue.”

Horner added: “It raised some questions he had to deal with. He went back to basics and drove a kart in the middle of the year to get back to the bare essence of why he was a grand prix driver and rediscovered his passion for being a grand prix driver.”