Ricciardo has exceeded expectations, according to Red Bull F1 boss

Ricciardo has won two races and comfortably outscored illustrious team-mate Sebastian Vettel in the first 11 races of the season.

"Daniel has done a wonderful job, he's exceeded all of our expectations, and probably even his own, to have been so quick so soon," Horner told AUTOSPORT.

"But it's not just his speed, it's his racecraft, his ability at the high-pressure points in qualifying and the race, when he has delivered and it has all looked very easy for him.

"He has been right up there and his race in Germany against [Fernando] Alonso was fantastic.

"The fact he wouldn't give him and kept fighting shows that behind that big smile is a really steely, determined racer."

Ricciardo has also played an important role in keeping the Red Bull team's spirits up during a difficult season.

"The enthusiasm that Dan has brought into the team has been positive for everyone," said Horner."

"It has been great for the team, especially when things are tough.

"Then, the team looks to its drivers in many respects [for a boost] because they are the ones that have to deliver on a Sunday afternoon."

Horner also believes that the relationship between Ricciardo and team-mate Vettel is proving to be a productive one.

"His relationship with Sebastian is strong and it's great to have two drivers that are feeding each other.

"There's a rivalry on track, but off track they are working as hard as they can and as openly as they can with each other to try and improve the car."