Red Bull team principal Christian Horner has warned Lewis Hamilton he would be “foolish” to underestimate Daniel Ricciardo as a title contender.

Hamilton was quoted in Motor Sport magazine as saying the four strongest drivers this season were himself, Sebastian Vettel, Max Verstappen and Fernando Alonso. With Ricciardo not getting a mention despite finishing ahead of his teammate in the drivers’ championship, Horner says Hamilton needs to be aware of the threat the Australian would be in a championship fight.

“Lewis would be very foolish to underestimate Daniel,” Horner told Sky Sports News. “He’s a phenomenal driver, he’s arguably the best overtaker in the business. He’s driven some great races this year and some great races in his time at Red Bull.

“He’s absolutely ready for a championship challenge if we can provide him with the tools to do the job.”

And Horner feels Red Bull was close to being a title contender this season but for reliability issues, despite finishing 154 points behind Ferrari and 300 adrift of Mercedes in the constructors’ championship.

“If you look at the number of points we have given away through unreliability, it’s close to 160,” he said. “Engine reliability has hit us really hard. At the beginning of the year we undelivered on the chassis, we didn’t hit the ground running. We understood those problems quickly and moved to address them quickly.

“We will take all the lessons from this year into next year and we have a lot to be optimistic about. We are hopeful that the engine situation will improve and we are getting a lot of promises that will be the case.

“But what’s been really encouraging is the last 25 percent of the season. We have had one of, if not the, strongest cars. If we can take that on RB14, we can give Merc and Ferrari a closer fight.”

On Thursday, Ricciardo praised Hamilton’s ability to stay calm under pressure when discussing what swung this year’s title battle against Vettel in the Briton’s favor.