Doubts over Nick Kyrgios' fitness remain despite finally hitting the court at Kooyong on a day of intrigue, giving rise to a possible shock Davis Cup comeback by Australian great Lleyton Hewitt.
Kyrgios has been laid low by a mystery virus, sparking speculation Sam Groth or even the recently retired Hewitt could be pressed into singles service on Friday when the first-round tie against the United States begins.
The 20-year-old took regular breaks on Wednesday during a 40-minute practice session, sitting with a towel over his head in sweltering late-afternoon heat in Melbourne.
While he moved well during the hitout, he did little to dispel fitness doubts while leaving the court, refusing to speak to reporters.
Kyrgios' mother Nill did speak, describing the "terrible" virus her son had dealt with since pulling out of last week's semi-final against Stan Wawrinka in Dubai.
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"He's a bit tired, he's still getting over the virus - he's trying his best.
"It was hard to get him here ... I think around the boys, it's going to be a discussion (about whether he'll play).
"I can't say (but) I think he hit pretty well."
Coach Jason Stoltenberg was encouraged by the session but earlier left the door ajar for a possible Hewitt return.
"... He's enjoyed the hitting ... he thought he was retired and he's been hitting more than these guys.
"It's probably the first time that a captain has actually had to get out and prepare as if he may play. He's a great team man and he'll do whatever he needs to do - whether that's playing or sitting on the side. We don't expect that he'll play but we'll have to wait and see over the next 24 hours.
"He's a thinker, he thinks ahead and he's pretty organised. I'd say that ... he's just covering all of his bases."
Groth - who will partner John Peers in Saturday's doubles - is ready to step in should Kyrgios (back/hip/virus) or Bernard Tomic (wrist) be forced out of Friday's opening singles.
"I'm definitely ready and, if that chance comes for me, then I'm definitely excited about it as well.
"Obviously, I'm doing a lot of my doubles stuff but if one of those boys, for any reason, is not ready for Friday or Sunday, then I've put myself in a position where I can play singles - especially on a grasscourt in a Davis Cup environment where I've done well before."
Champion American doubles duo Bob and Mike Bryan also practised on Wednesday.
Asked about the Hewitt prospect, Mike Bryan said the move wouldn't surprise his team.
"... He's been playing a lot of singles and doubles, so we're going to be ready for anything.
"But if he plays for Australia, it won't be a bad choice for the Aussies - he's a legend and he'll step up just fine."
Both teams must submit final line-ups on Thursday morning.
