The AlphaTauri driver suffered a metacarpal fracture in practice for last month's Dutch Grand Prix, ruling him out of the Italian Grand Prix one week later as the Australian underwent surgery in Barcelona.
Horner, whose team has loaned out third driver Ricciardo to sister squad AlphaTauri, says Ricciardo's recovery is going to plan but he believes the next double header on the calendar in Singapore and Japan is going to come too soon for the 34-year-old.
“Certainly Singapore, I don't think there's any chance he'll be ready for then. I think it would be optimistic for Japan," Horner said when asked for a timeline of Ricciardo's return.
"But I think his recovery is going well, he's got obviously immobility of the hand and he's into rehabilitation now.
"We’ve seen with motorcyclists rushing comebacks can sometimes do more damage, so I think that we just want to make sure he's fully fit before he gets back in the car.”
Source: Autosport