Zak Brown thinks it will be "very difficult" for Fernando Alonso to win the Indy 500 later this month.
Alonso almost won in 2017, but that was in a McLaren entrant that was run by Michael Andretti's experienced team.
"I think the challenge we have taken on is great," Brown, the McLaren boss, said in Barcelona.
"Starting a team is much more difficult than what we did in 2017. The teams that are there are as good as they can be. I don't think it's easy for us at all.
"Can we win?" he added, according to Marca sports newspaper. "We can, but I think it will be very difficult."
Alonso travels to Indianapolis on Sunday to start preparing for Indy 500 qualifying.