Andy Murray revealed his soft side at the US Open yesterday when he expressed his love for animals but he will need to harden up today when he tries to shrug off a cold and a tricky opponent in the third round.

The Scot takes on Brazil’s Thomaz Bellucci for a place in the last 16, battling a cold that has affected his voice but not, he says, his desire and belief that he can win the title for a second time.

The emotional energy required to fight back from two sets down in the previous round against Adrian Mannarino of France will not have helped but the resolve he showed can only be of benefit.

Like many players here this week, with some blaming air conditioning as the culprit, Murray says he’s not quite 100 per cent and is not taking anything for it, other than vitamin C.

“The doctors that are here and part of the Tour can prescribe you stuff that’s fine, but there’s no real cure,” he said. “Hopefully it takes three or four days before it’s out the system. That’s one of the things about being an athlete. It’s survival of the fittest. There’s not much you can take.

“I’ve been feeling it at the beginning of the matches a little bit. But after the first couple games, I feel fine really. But I think quite a few of the players have had a head cold a little bit. My brother [Jamie] was quite sick yesterday, as well. I think there's a few of the players have had it.”

Bellucci is the last left-hander, other than Rafa Nadal, to beat Murray, having come out on top when they met in Madrid in 2011, in the kind of “lively” conditions that Bellucci enjoys.

“I don’t know if he grew up at altitude but he likes it when the conditions are pretty lively, like they are here,” he said. “He’s obviously playing well, he won his first couple of matches.”

Murray’s love for animals is well known and he’s been sporting a World Wildlife Fund patch, something he said, is dear to his heart.

“I care as much about animals as I do about human beings,” he said. “Some people find that funny, I don’t find it funny. I just think that we’re all on this planet together and it’s horrible when you see what happens to some animals that are almost extinct.

“There was that story about Cecil the Lion a few weeks ago. It’s horrible. Anything you can do to help. They don’t have a voice, human beings do, it’s nice to try to help with that.”

On the court yesterday there was something of a vintage performance from Venus Williams, who won the first of her two titles in 2000. Her opponent yesterday, Belinda Bencic, was only three at the time but the Swiss went into the match perhaps as a slight favourite, having beaten Serena Williams on the way to the title last month in Toronto.

Williams ripped through the first set and then recovered from 4-1 down in the second to clinch a 6-3, 6-4 victory.

“It’s always a balance for me between being aggressive and not making errors but I’d rather make an error but going for it,” Williams said.

“She’s tenacious so I’m really pleased I played a good match against someone who’s had such a good summer. But it’s wonderful to be here, I love the US Open, I love how everyone got behind me when I was down, it was a wonderful feeling.”

Bencic, who was seeded 12, said she had simply been outplayed. “I think she was just too good,” the Swiss said. “I didn’t have enough time to make the rallies.”

Defending men’s champion Marin Cilic scraped into the fourth round with a 6-7, 7-6, 6-3, 6-7, 6-1 victory over Mikhail Kukushkin of Kazakhstan.

Britain's Jo Konta takes on Andrea Petkovic of Germany in the third round of the women's event.