McLaren could be looking to return to Mercedes power.

Days ago, Carlos Sainz surprised some in the paddock by saying he "expected more" from Renault's latest engine upgrade.

"There have been three engine evolutions," he said. "I didn't notice the first or the second ones either."

Then at Spa, both Sainz and Lando Norris had engine problems, prompting Spaniard Sainz to be critical of Renault once again.

"These two situations are a little unacceptable, so you will have to talk to Renault about that," he said.

Recently, new McLaren team boss Andreas Seidl said of the team's engine supplier situation: "In 2020 we have a contract and we will continue with Renault.

"For 2021, we will see."

But the Spanish sports newspaper Marca speculates that McLaren could be positioning to secure a customer Mercedes deal, taking over from struggling Williams.

As for the problems at Spa, Seidl said: "We are all in this together and need to analyse what happened.

"Of course it's disappointing to have two retirements, including a car that could not start the race. But Renault is doing a big effort to get more results this season and that is encouraging.

"It's disappointing to have penalties and dropouts, but it's important to have a transparent relationship so we can look at these issues and solve them together.

"But it was not a problem of excess mileage or the end of engine life, nothing like that," he added.

Marca said McLaren cannot return to Honda power, because Red Bull negotiated an exclusive deal for five years.