Cape Town - Andy Murray admitted that it's "obviously not an easy thing to do" after winning his second Olympic gold medal with victory over Juan Martin Del Potro on Sunday.
The Scot, representing Great Britain at Rio 2016, became the first man to win a consecutive gold medal in tennis with a 7-5, 4-6, 6-2, 7-5 victory over the Argentine.
"It's obviously not an easy thing to do," he said. "I had to fight unbelievably hard tonight to get it.
"To defend the singles title... I think Venus and Serena (Williams) have won about four each but haven't defended a singles title before."
The 29-year-old was inevitably asked about Tokyo 2020, but insisted that he is keeping his focus on the immediate future rather than thinking about a potential third Olympic medal.
"Four years is a long time and so many things can change. A lot has changed since 2012, I'm happy here competing for the biggest events. Who knows about Tokyo in four years. At 33, I'm not sure I'll be at the same level."
"I'll enjoy this one for the next couple of days but I'm supposed to be playing a match on Wednesday in Cincinnati. I'll try and get there as early as I can and hopefully recover a little bit over the next couple of days."
The Scot, representing Great Britain at Rio 2016, became the first man to win a consecutive gold medal in tennis with a 7-5, 4-6, 6-2, 7-5 victory over the Argentine.
"It's obviously not an easy thing to do," he said. "I had to fight unbelievably hard tonight to get it.
"To defend the singles title... I think Venus and Serena (Williams) have won about four each but haven't defended a singles title before."
The 29-year-old was inevitably asked about Tokyo 2020, but insisted that he is keeping his focus on the immediate future rather than thinking about a potential third Olympic medal.
"Four years is a long time and so many things can change. A lot has changed since 2012, I'm happy here competing for the biggest events. Who knows about Tokyo in four years. At 33, I'm not sure I'll be at the same level."
"I'll enjoy this one for the next couple of days but I'm supposed to be playing a match on Wednesday in Cincinnati. I'll try and get there as early as I can and hopefully recover a little bit over the next couple of days."