Sir Lewis Hamilton accused Carlos Sainz of brake testing him during the Singapore Grand Prix on Sunday.
The Briton started third after a sensational qualifying performance on Saturday, but he was passed off the start of the race by the Ferrari.
Hamilton felt that Sainz had pushed him off the circuit to get ahead, but the stewards did not think that was the case, so no action was taken.
However, the seven-time champion kept the pressure on the 28-year-old, and a Safety Car, as well as two virtual ones, enabled him to stay even tighter to the Italian car in front.
During the latter of the two virtuals, Hamilton was applying the blowtorch to the back of Sainz, as they both tried to guess when the light would turn green.
As the pair jostled for the best possible starting position when the Virtual Safety Car was brought back in, Hamilton felt as though the Spaniard had braked a little too sharply.
“He just brake tested me,” he said on the radio.
The 37-year-old went on to make a mistake while chasing down Sainz, going straight on at Turn Seven and colliding with the barrier, but he was thankfully able to continue.
Hamilton would then make another slight error when trying to pass Sebastian Vettel for P7, and lost out to Max Verstappen, who himself had made an error while attempting a move on Lando Norris on the second Safety Car restart.
The Briton came home ninth having started up in third, in what was a disappointing day for Mercedes.
Team-mate, George Russell, had even worse fortunes, starting from the pit lane after taking a new engine following his elimination from Q2 on Saturday.
Russell ended up in contact with Valtteri Bottas early on, then again with Mick Schumacher towards the end of the evening, and he finished 14th and last of the classified runners.
The silver lining for the Silver Arrows though, was that Russel grabbed the satisfaction of taking the fastest lap late on.