Mark Webber believes Michael Schumacher was "pushing the boundaries" during his fight with Lewis Hamilton at the Italian Grand Prix.
The seven-time champion was involved in an intense battle with the McLaren driver in the early parts of the Monza race while they battled for third position.
Schumacher's driving was labeled as "pretty harsh" by McLaren team boss Martin Whitmarsh after the German changed lines more than once to defend his position.
Red Bull driver Webber said Schumacher's driving was not what other racers understand to be acceptable and believes the German was pushing the limits with his defense.
"It was a unique fight between Michael and Lewis because the McLaren was running up against the rev limiter, so Michael had a speed advantage on the straights," Webber wrote in his column for the BBC.
"He could position his car very cutely to try to keep him out. There were a few times when Michael returned to the normal line having defended. That's the point of interest because it's not what most drivers understand to be acceptable.
"One incident in particular stood out – out of the second chicane and into Lesmo, when Lewis had a clear run and Michael went across to defend and then came back again. Moving that many times was pushing the boundaries."