It may not come as that much of a surprise to anyone who has followed the career of Andy Murray, but the world No.4 admitted yesterday that he has a problem: a swearing problem.

It is not that the Scot cannot stop swearing – he did concede that sometimes he forgets where he is – but rather that he and other English speakers are being penalised more than their overseas counterparts.

Murray, who today plays the Frenchman Richard Gasquet for a place in the quarter-finals of the Rome Masters, was warned for an audible obscenity during his hard-fought win over David Nalbandian on Tuesday night.

Murray admitted he deserved the warning but suggested that players who swore in other languages were often dealt with more leniently than English-speakers. "I swear on court regularly," he said. "I try not to, but sometimes you forget where you are and what's going on. It's a mistake and something I try not to do.

"But I also understood a lot of the stuff he [Nalbandian] was saying from my time in Spain. But because what I say is in English, we're always the ones to get the warnings. I don't think what came out of my mouth today was anywhere near the translation of the things he said. But it's not right to do it and I deserved a warning."

Many of the umpires are multi-lingual but they are also given a long list of swearwords to look out for in a number of languages by the ATP Tour and then urged to use their discretion. When he does swear, it seems Murray annunciates too clearly and, yesterday, he received the backing of Roger Federer, who said the umpires should be consistent no matter the language.

"It's like the coaches on the women's tour who go out and talk to their players," he said. "It's an advantage for those who can speak in their native language to their players, so basically no one understands. Maybe you shouldn't swear but who cares? Sometimes it's to yourself. It happens."

Federer admitted he had a few aches and pains after winning the Madrid Masters title last weekend and only decided to play here after his morning practice. Yet the Swiss was still too good for Carlos Berlocq of Argentina, winning 6-3, 6-4 to set up a meeting with the former world No.1, Juan Carlos Ferrero.

Rafael Nadal, overtaken by Federer in the rankings last weekend, was in ruthless form as he crushed Germany's Florian Mayer 6-1, 7-5.

In the women's event, Serena Williams made it two wins in the space of 18 hours as she battled back to beat Russia's Nadia Petrova 4-6, 6-2, 6-3, but there were defeats for world No.3 Agnieszka Radwanska and former No.1, Caroline Wozniacki.

n Elena Baltacha, the British women's No.1, will take on Poland's Urszula Radwanska today for a place in the quarter-finals of the ITF $100,000 Sparta Prague Open, with her confidence on the rise once more.

The Scot described her 6-3, 6-1 win over the Spanish teenager Lara Arruabarrena-Vecino as "probably the best match I've played this year".

"The last few months have been a battle because I've been playing well in practice but just not getting the wins," she said. "It really clicked today and I just felt really in control all the way through."