The second practice session for the US Grand Prix at the Circuit of the Americas bore witness to what could be expected during the race. Title rivals Max Verstappen and Lewis Hamilton already got on each other's nerves as they found themselves racing side-by-side down the pit straight during the practice session.

Verstappen's Red Bull and Hamilton's Mercedes zipped through the entire straight side by side almost to the millimeter. When they reached the turn, Hamilton took the corner as Verstappen backed off while calling the seven-time world champion a "stupid idiot" over the radio.

The championship leader's race engineer, Giampiero Lambiase, responded by telling him to simply ignore Hamilton, but Verstappen made sure he gave Hamilton a piece of his mind via a raised finger.

The tension is palpable around the circuit, as the crucial stage of the season comes around. Verstappen leads the championship by only six points going into this weekend, and everyone knows that it only takes one bad result to flip the coin in Hamilton's favour.

The lead has been going back and forth between the two drivers all season, with neither being able to extend the gap. The Mercedes are expected to do well in the remaining six races in 2021, but Red Bull has proven predictions wrong numerous times already.

Hamilton has also made uncharacteristic mistakes this season, showing that the challenge by Verstappen is pressuring him much more than he lets on.

About the incident on Friday, Verstappen said that he did not understand what Hamilton was trying to do. "We all line up for a fast lap. So I don't quite understand what happened there."

The Red Bull and Mercedes cars appear to be evenly matched throughout practice, and fans are surely in for a wild ride in Texas on Saturday and Sunday.

Lewis Hamilton
Lewis Hamilton (L) and Max Verstappen crashed out of the Italian Grand Prix after colliding with one another ANDREJ ISAKOVIC/AFP