Mercedes facing unexpected problem after powerful Sao Paulo GP start

Mercedes has admitted both George Russell and Kimi Antonelli are battling understeer for the first time since the team's major upgrade package landed in Malaysia, despite Antonelli topping Friday's second practice session at Interlagos.

The Italian set the pace with a 1:10.763, edging out Lando Norris and Max Verstappen, with Russell fourth fastest as Mercedes continued to look competitive on Friday. 

But Mercedes' deputy team principal Bradley Lord struck a cautious tone when discussing the car's underlying balance, pointing to a handling trait the squad had not seen since introducing its seven-part aerodynamic update at Sepang.

Speaking after FP2, Lord said the Silver Arrows look in the fight but that understeer needs dialling out for both drivers.

"Real progress is hitting the ground running with the car," said Lord. "Both drivers are still looking to dial out some understeer, which is not something we've had too much of since we put the update package on in Malaysia. 

"So, overall, long-run pace looks in the mix with Lando [Norris], Max [Verstappen] and both of our guys. So maybe Ferrari are half a step behind, but I'm sure they'll come good as well in the hotter conditions."

Has Mercedes finally understood Malaysia upgrades?

Conditions at Interlagos on Friday turned changeable, with air temperatures dropping below 20 degrees Celsius during FP2 and light drizzle disrupting tyre warm-up. 

Saturday is forecast to be considerably warmer, before temperatures fall again on race day, a swing Lord suggested would offer a genuine test of how well Mercedes understands its new aerodynamic package across varying track conditions.

Asked whether the operating window of the upgrade is becoming better understood within the team, Lord was candid about the uncertainty that remains.

"That's a good question," said Lord. "I'm not quite sure how we would answer that, to be honest. We'll see. 

"This weekend we've got a great test of it, with cool conditions [on Friday], much warmer on Saturday and then cool again on Sunday, and whether we can cope with that sort of adjustment in track temperature and what it does to the balance as well."