Kimi Raikkonen says a pulled muscle led to the Alfa Romeo Formula 1 team calling up Marcus Ericsson as a potential Belgian Grand Prix stand-in but he expects to race.
Ericsson, who has remained Alfa's reserve after losing his race seat with what was then Sauber at the end of last season, is skipping this weekend's Portland IndyCar round to be present at Spa.
Sources had suggested this was due to a specific concern over whether Raikkonen would be available for the race.
The Finn confirmed this was the case in the Spa paddock on Thursday.
"I pulled a muscle and that's about it," said Raikkonen. "We will see what happens.
"Obviously we need to have some back-up plans. It would be stupid not to have our third driver in case I couldn't be driving, then it is the worst-case scenario.
"It is a difficult situation for him [Ericsson] also because he had a race, but that is how it is.
"I would say it is getting better, so we will see how it is.
"Obviously it is impossible to drive [to test it]. We have simulators but that doesn't tell an awful lot.
"We will see how it is but in my head it should be fine."
Raikkonen only elaborated on how he had sustained the injury by saying he had been playing "sport".
Ericsson is bidding to secure a new deal to continue in IndyCar for 2020, but skipping the Portland race for an unnecessary appearance at Spa represents a frustrating interruption to his efforts in the United States.
Ericsson will be replaced in the Schmidt Peterson Motorsports IndyCar line-up by Conor Daly for this weekend's race.