Daniel Ricciardo back to his best, says Red Bull F1 boss Horner

After scoring three grand prix wins during his debut campaign with Red Bull last year, Ricciardo and the team have struggled these past few months, notably with regard to numerous engine issues involving supplier Renault.

Ricciardo and team-mate Daniil Kvyat had a morale boost in Hungary last weekend as they finished third and second behind race winner Sebastien Vettel's Ferrari, with Ricciardo having had a shot at victory before an incident with Mercedes' Nico Rosberg.

Giving Ricciardo an "A-plus" in terms of a half-term report, Horner added: "Daniel can always improve in some areas, of course you can.

"But he's at the top of his game, and with some of his overtaking moves on Sunday you could see he was back to the best we've seen of him."

Kvyat, in particular, has raised his game since a warning from Red Bull advisor Helmut Marko following the Spanish Grand Prix in early May.

Marko suggested Toro Rosso duo Max Verstappen and Carlos Sainz Jr were doing a better job, claiming "the established guys need to look out".

Since then Kvyat has finished fourth in Monaco, sixth in Britain, with his second in Hungary making him the second youngest driver in F1 history to stand on the podium.

"He had a slow-ish start, which wasn't really all his fault," assessed Horner.

"He missed the first grand prix, he had lots of reliability issues and failures, and it could have got into his head a lot more than it did.

"Testimony to him - he bounced back from it and got himself going. So it's a very positive report for him going into the summer break.

"I think since Monaco he's just made more and more progress.

"He did a really good job in Hungary and deserved his first podium. That's another tick in the box for him.

"He'll draw confidence from that, and it's part of an upward trajectory for him that he's developing very nicely."