World No 6 Taylor Fritz may not be at full fitness for this month's Australian Open after the American said a niggling knee issue had prevented him from pushing too hard in his season-opening defeat at the United Cup.
The 2024 US Open runner-up cut a frustrated figure in Saturday's 4-6 7-5 6-4 loss to Argentine Sebastian Baez in the mixed team competition in Perth and said he may need a spell on the sidelines to fully recover.
"It's not the way I want to start off the year. There's definitely a lot of rust showing," said Fritz, who is expected to be one of the main contenders for the title at the first Grand Slam of the year at Melbourne Park.
"I spent the majority - pretty much the entirety of the off-season - trying to rehab my knee tendinopathy, but that's a thing that takes months and months to get better.
"I didn't get to play a lot of points because I'm trying to not push it too hard," he told reporters.
Fritz said he would try to get more time on court while managing the knee issue.
"But if that doesn't work in a couple of months, then I am just going to have to full stop and fix it."
The Australian Open runs from January 18 to February 1.