Red Bull Racing will be concerned about Mercedes' straight line speed going into the United States Grand Prix at the Circuit of the Americas this weekend, according to former Formula 1 driver and Sky Sports commentator Martin Brundle. The Silver Arrows team have shown an upturn in pace in the last two races, and it is not expected to be coming just from their upgraded power unit.

Max Verstappen may be leading the Drivers' championship by six points with six races remaining in the 2021 season, but Mercedes are the team with the momentum at the moment. Lewis Hamilton triumphed at the Russian Grand Prix, while Valtteri Bottas took the chequered flag first in Turkey.

Verstappen was fortunate to finish in second at Sochi despite starting at the back of the grid, while in Turkey, he finished second albeit over 14 seconds behind race winner Bottas. Despite the Austrian team recording a double podium finish in Istanbul, it was a strange weekend for Red Bull, who had no answer to Mercedes' race pace.

''Red Bull will be concerned. Lewis didn't exactly cruise past Yuki Tsunoda early on in the AlphaTauri. Nor did he ease quickly past Sergio Perez in the other Red Bull. But the Mercedes has shown great straight line speed as well," Brundle said, as quoted on GP Blog.

"I think Istanbul was more that Red Bull had a bit of an off weekend as well to compound the issue. There are some concerns in the Red Bull camp, that Mercedes have found some real pace and I think it's to do with the aerodynamics."

The Circuit of the Americas have generally been a Mercedes stronghold with Hamilton taking six wins since the opening race in 2012. Kimi Raikkonen beat the Briton to the win in 2018, while Bottas took the win at the last race in 2019.

However, Red Bull have been on the podium consistently, and this is the first time in quite a few seasons that the Austrian team have produced a car that can consistently challenge the Mercedes. Therefore, there is a possibility that Verstappen can spring a surprise if they get their set up right and can challenge Mercedes for raw pace.

Max Verstappen
Red Bull's Max Verstappen was a winner in Austria last year William WEST/AFP