Fernando Alonso will miss the first practice session at the Hungarian Grand Prix on Friday, with Aston Martin Formula 1 reserve driver Felipe Drugovich replacing him.
Aston Martin said that Alonso has been "managing a muscular injury in his back" since last weekend's Belgian GP and treatment has continued on Friday morning.
A decision on Alonso's participation in FP2 "and the remainder of the weekend" will be made "in due course".
The team's chief trackside officer Mike Krack said that Aston Martin "elected to just increase the recovery time and drop out FP1, which is normally the least important session".
"I don't think it's the hours," he added. "It's probably more the lower amount of laps [that will help Alonso]."
Drugovich, the 2022 Formula 2 champion, has been on the brink of his F1 debut before. He deputised for Lance Stroll in pre-season testing in Bahrain in 2023 as Stroll recovered from an accident, and was on standby for that year's season opener.
However, when Stroll withdrew from this year's Spanish GP, it came too late in the weekend for Drugovich to step in.
Drugovich has tested at the Hungaroring in the past as part of previous old-car running with Aston Martin. He has also driven this year in the team's Pirelli tyre test obligations.
The fact Drugovich will replace Alonso immediately in FP1, rather than Alonso attempting to drive, and Aston Martin's admission that a decision does need to be made, suggested there was a serious possibility of Drugovich continuing for the rest of the weekend.
But Krack played down that likelihood of that happening.
"We have obviously made some modifications, on his seating position," said Krack of the changes Aston Martin had made to accommodate Alonso.
"We have checked some stuff yesterday [Thursday], how to make it more comfortable for him. So we are quite confident he will be fine."
Drugovich is a candidate for an F1 seat at Cadillac next year, and a grand prix debut in which he performs strongly would aid that bid.
Alonso had remarked of Drugovich only on Thursday that it would be "great to see him in Formula 1".
"He has an incredible talent," said Alonso.
"Formula 2 was the demonstration, but we can see it here every day when we work with him and the simulator work, some of the free practices that he has and he has been always delivering the performance that the team was asking, even with very limited kilometres.
"It will be interesting to see him in a full-time drive and I hope it happens."
