Red Bull: Verstappen stronger after riding storm of early F1 2018 woes

Verstappen had a troubled start to 2018, and was criticised for over-driving and a lack of maturity after a spate of incidents.

But Verstappen has made huge strides in the second half of the campaign, and last weekend charged flawlessly through the field in the US Grand Prix at Austin from 18th on the grid to finish second.

"I think really since Montreal he has driven some brilliant races," said Horner, when asked by Autosport about Verstappen's turnaround.

"He had a tough start to the year. He didn't let his chin drop. He didn't let the pressure get to him.

"He rode the storm and emerged the other side. I'm sure it only made him stronger. And he has got a pretty decent level of experience now, that he is putting to very good use.

"I think he is becoming more and more rounded in all areas. We just need to give him the tools to do that kind of performance every weekend."

While Verstappen's season has gone from strength-to-strength, his team-mate Daniel Ricciardo has hit a run of difficulties and retired again in the US.

An energy-store failure put Ricciardo out of a race he could well have won, and the Australian made his feelings clear by punching a hole in the wall of his drivers' room after he returned to the paddock.

Horner said Ricciardo's action was understandable given his recent run.

"You can't blame him, the frustration that is in him," said Horner.

"What's ironic is that it is always on his car it seems. It was the other way around last year with Max.

"As Renault's premier driver you wouldn't expect these issues to be happening.

"From a team point of view, all we want to do is finish the year on a high with him and have the chance to celebrate the time he has been with us. But it's a bit unfortunate these things are still happening for him.

"There must be frustrations within him with the issues that are happening. He knows it's not the team's issue, he knows it's nothing we have done and he cannot get his head around why it keeps happening to him."

Verstappen's charge to second has lifted Red Bull's hopes of ending the year strongly, but Horner said the team's current power deficit with Renault's engine means this weekend's Mexican GP is its last proper chance of a win.

"We are hoping that with the altitude of Mexico it will concertina the engines a bit," said Horner.

"That Ferrari and Mercedes will not be able to run their high power modes, that is what helped us last year.

"We are hopeful that it will be the same again this year, and realistically it is our last shot at winning a race between now and the end of the year."