Marika Koroibete's Wallabies future has been plunged into further doubt, with coach Joe Schmidt refusing to guarantee the winger would return to the Australian team.

Koroibete was left out of the 34-man Spring Tour squad, with Schmidt saying the two-time John Eales Medallist was "flat" and "having a break".

There was better news for former captain Will Skelton, who has expressed his desire to be back in the fold and officials are hopeful he will face the British & Irish Lions next year.

But when fellow NRL convert Joseph Aukuso-Sua'ali'i was named in his maiden Wallabies squad, it emerged Koroibete could have played his last Test.

The 32-year-old Koroibete missed last month's second Bledisloe Test through injury, amid questions over his spot after an underwhelming Rugby Championship.

"He's just having a break. He probably felt he wasn't at the very top of his game, and he was a little bit flat after the season he had," Schmidt said on Tuesday.

"He is required to be back and training with (Japanese club) Panasonic reasonably soon.

"He's not a player we own, and that is one of the flexibilities you need to have with these guys.

"In the absence of Marika, I thought Dylan Pietsch was super in that last Test in Wellington."

Koroibete's absence came as Sua'ali'i and Harry Potter were both picked as possible debutants on the wing in Australia's squad for the four-Test tour of the UK.

Pietsch, Andrew Kellaway and Max Jorgensen are also in the squad.

Asked if Koroibete would ever add to his 59 Tests, Schmidt would not guarantee it.

"They are discussions that will probably take place in March or April next year and see how he's going," Schmidt said.

"I watch his Panasonic games, I know (his coach) Robbie Deans well enough to have a chat with Robbie as well and see how he is tracking.

"At the same time, we have got some young wingers starting to come through and put some pressure on."

While Koroibete will go straight into Panasonic's pre-season, fellow back Samu Kerevi will be available for Australia's first three Tests before returning to Japan.

Former captain Skelton will also play the first three Tests before returning to club duties in France, after the club-versus-country scenario ruled him out of the Rugby Championship.

Schmidt said he had not yet spoken to Skelton about whether he would be available for the Lions tour of Australia next winter, but was hopeful the lock would feature.

"We haven't talked about the Lions to be honest," Schmidt said.

"He's keen as mustard (to play these Tests). He doesn't take any convincing to play for the Wallabies.

"It's one of those things that if we didn't get Will and Samu involved in this window, I think it would be very difficult to have them involved in the Lions.

"This is part of an investment for that."

AAP