Daniel Ricciardo facing time away from F1 after wrist injury may require surgery
The experienced Australian, who had been preparing for his third race with AlphaTauri after making a comeback as replacement for dropped Dutch driver Nyck de Vries (28), crashed in Friday's second session at Zandvoort.
"He's headed off today to Barcelona, they may even have a little operation on him tomorrow to just tidy up where that break is," Horner told Sky Sports television of Ricciardo's next steps.
Barcelona-based MotoGP traumatology specialist Javier Mir is renowned for his work and operated on Aston Martin's Lance Stroll (24) when the Canadian broke his wrists before the start of the season.
Stroll was able to race in Bahrain two weeks later.
"It's quite a clean break and then of course it's all about the recuperation and how long that takes. Any normal human being would probably be about 10-12 weeks but we know that these guys aren't normal," said Horner.
"So it will all be about the recovery process... Is it going to be three weeks, is it a month, is it six weeks? Nobody really knows."
The Italian Grand Prix at Monza would appear to be a non-starter, coming the weekend after Zandvoort, with Singapore then on September 17th and Japan on September 24th.
Ricciardo sat out the first 10 races of the season after initially planning to take a year out after an unhappy stint at McLaren but had said on Thursday that he was re-energised and motivated again.
"The thing he was most frustrated about talking with him last night was he's just taken a bunch of time off, just got his mojo back, getting back into it and now he's on the bench again," added Horner.
"I'm sure at the back of his mind he's probably got Singapore as a target. But then again Singapore's probably one of the toughest circuits on the calendar. Nature will take its course."
New Zealander Liam Lawson (21), the Red Bull-owned team's official reserve, has been called up to replace the eight-time grand prix winner and will make his F1 race debut on Sunday.
Lawson was 18th fastest in final practice, bringing out red flags with a late spin, but Horner said nothing should be read into that.
"Not even a dry track, horrible conditions, a slippy circuit, a track that bites if you make a mistake," said the Briton.
"He looked pretty wide-eyed last night but I have to say I think he's done a pretty mature job so far. It's just seat time. He just needs more time in the seat and it would be unfair to judge him in this (practice)."
