Ajla Tomljanović in doubt for Australian Open after first set retirement against Maya Joint

Ajla Tomljanović's Australian Open campaign is in doubt after she retired with injury against Maya Joint in the Adelaide International round of 16.

Tomljanović was dominating at 2-0 and was leading 30-0 on her serve. However, she started to fade and at 30-30 clutched at her shoulder.

Her service speeds were noticeably down, with Sam Smith saying they'd "collapsed".

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"I think she'd have the trainer here, I wouldn't hesitate," Smith said on Nine's commentary.

At deuce, Tomljanović grimaced and then decided to sit down with a call made for medical attention.

"She only calls for the trainer if something serious is going on," Smith said.

"Can't believe this, she's in amazing shape and hitting the ball beautifully."

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The trainer took Tomljanović through specific shoulder exercises before they both went into the dressing room.

The 32-year-old reappeared and retired, giving Joint a hug before the Aussie teen passed on her best wishes.

"It's bad timing really, I hope she can get better for the AO," Joint said post-match.

"I was looking forward to this match, so many people came out here today, I know it would've been a good match but I hope she can get better fast."

Joint will now play Mirra Andreeva in the quarter-final on Thursday at 7pm (AEDT).