Mercedes engineering director Aldo Costa has played down his boss' claim of a "setback" with the team's 2019 engine.

At the FIA gala, Toto Wolff suggested the defending world champions were struggling to reach their lofty performance targets with a new power unit concept on the test bench.

Many rather saw the Austrian's comments as an early attempt at mind games and certainly nothing serious and now Costa has rather confirmed that suspicion.

"I think it was a bit misunderstood," he told Italy's La Gazzetta dello Sport.

"When you put a new engine with new concepts on the bench, there may be something that doesn't work. But it's nothing dramatic."

Costa himself is to step back from his current role at the end of the year, remaining just an advisor to Mercedes from next season onwards.

And looking ahead to the challenge the German manufacturer faces in 2019, he is expecting a three-way title battle.

"Ferrari will obviously be there to fight with us, and I am also expecting Red Bull, considering that they always speak good things about the new Honda engine," he said.