Horner: Injured Ricciardo could miss Singapore and Japan GPs

The Australian suffered the injury in practice for last month's Dutch Grand Prix and had surgery in Spain on August 27th.

New Zealander Liam Lawson replaced Ricciardo at the Red Bull-owned sister team at Zandvoort and in the Italian Grand Prix at Monza last weekend.

"Certainly Singapore, I don't think there's any chance he (Ricciardo) will be ready for then. It would be optimistic for Japan," Horner told reporters.

"We've seen with motorcyclists rushing comebacks, they sometimes do more damage so I think we just want to make sure he's fully fit before he gets back in the car."

Horner said Lawson, who has been racing in Japan this year and would undoubtedly feel at home at Suzuka, had done a solid job.

"I think he's acquitted himself very well," he said.

Lawson finished 11th at Monza after 13th place in the Netherlands.