Fernando Alonso will not participate in the Bahrain Grand Prix on medical grounds following his accident in Australia, with McLaren reserve driver Stoffel Vandoorne set to deputise.
Alonso suffered a high-speed crash after hitting Esteban Gutierrez and was deemed unfit by FIA doctors during a routine medical check-up at Sakhir.
Vandoorne dominated last year's GP2 Series, securing the title with two rounds to spare, and will now fly in from Japan, where he was conducting pre-season testing ahead of a campaign in Super Formula.
"Following an examination undertaken this morning at the Bahrain International Circuit medical centre, it has been decided that McLaren Honda F1 Team driver Fernando Alonso should not take part in this weekend's Bahrain Grand Prix," read an FIA note.
"Two sets of chest CT scans were compared and it was decided that there was insufficient resolution of the signs to allow him to compete on safety grounds.
"A repeat chest scan has been requested before the Chinese Grand Prix and the results will be considered before allowing him to race there."
It is the second successive season in which Alonso has had to sit out a race, after he was not permitted to take part in Australia last year following an accident in testing.
"About to board for Bahrain, a bit earlier than expected but so much looking forward to it! Will do my very best for the team," said Vandoorne on social media.
"I tried until the last minute to race in Bahrain after the accident in Australia, they have been hard days logically after such an impact, but until the last second I try to race to help the team after the incredible work they have done this week," said Alonso.
"I understand the position of the FIA doctors and now I will try to help my team-mate Stoffel Vandoorne to make the most of the weekend. Thanks to everyone at McLaren-Honda."