Stan Wawrinka admits he is struggling with illness after the Swiss beat Lukas Rosol in the Australian Open third round.
Wawrinka, seeded fourth in Melbourne, could play Andy Murray in the semi-finals and he took one step closer by beating world number 51 Rosol 6-2 6-3 7-6 (7/3).
The French Open champion, however, was noticeably croaky in his post-match interview and confirmed he has been under the weather this week.
"Last few days I couldn't really talk. I've been OK, maybe too many cigars," Wawrinka said, smiling.
"I just had a little bit cold. I'm feeling better. As long as I'm moving well and feeling good on the court that's most important.
"I don't really need my voice, if I use my voice I talk too much s*** anyway."
Wawrinka showed few signs he was suffering on court as he eased past Rosol in just one hour and 55 minutes.
He now faces a fourth-round match-up against big serving Canadian Milos Raonic, who has made a strong start to the year after beating Roger Federer in the final of the Brisbane International earlier this month.
Wawrinka, however, has never lost to the world number 14 in four previous meetings.
"He's a tough player, for sure," Wawrinka said.
"I've never lost, but always been some tough matches. He's been playing really good since the beginning of the year, winning the first title in Brisbane against Roger in the final.
"I still think it depends a lot on my game, on what I'm going to do, on where I'm going to be on the court, the way I'm going to serve.
"In general, I always find some solution to break his serve, even (if it) is really tough."
Raonic also enjoyed a comfortable passage into the last 16 as he sailed past Serbia's Viktor Troicki 6-2 6-3 6-4.
After the match, Raonic dedicated his win to the victims of a shooting at a school in Saskatchewan, Canada on Friday, which left four people dead and several more injured.
"It was a difficult day back home," Raonic said. "There was a shooting in a high school in a small town. I give my thoughts to that community, the families, the students and the school affected.
"We wish you all the best. This win was for that community and a speedy recovery. All of Canada and the world is behind you."
Spain's David Ferrer will play American John Isner in the fourth round.
Ferrer beat another American Steve Johnson 6-1 6-4 6-4 while Isner overcame Spain's Feliciano Lopez 6-7 (8/10) 7-6 (7/5) 6-2 6-4.