Madison Keys refused to make excuses for her Australian Open semi-final loss, opting to instead pay tribute to Serena Williams.

An adductor injury has troubled the 19-year-old American, and her left leg was heavily strapped at Rod Laver Arena on Thursday.

Keys put up a fight before going down 7-6 (7-5) 6-2 to world number one Williams.

Asked about the injury, Keys acknowledged she was below 100 per cent " but insisted her 33-year-old opponent deserved all the credit.

"It [the adductor] is OK. It's not perfect. But, I had plenty of tape on it and I had plenty of medication. I did my best," she told a media conference.

Keys added: "I'm not going to sit up here and make excuses. So, you know, it was what it was. I did my best. She played really well. All credit to her."

Whether nerves were going to affect Keys in her first grand slam semi-final was the first question answered.

And it was a resounding 'no' as the teenager matched it with, and sometimes overpowered, her 18-time grand slam winner opponent.

Keys was proud of the way she handled herself, but said Williams' serve " which delivered 13 aces " was far too good.

"I think I handled the moment pretty well. I definitely had a good start, so nerves didn't totally play into that," she said.

"I thought I handled myself pretty well in that last serving game of mine.

"But, I mean, she played really well.

"She served really well. It was pretty much impossible for me to break her serve. So, you know, great job to her."