Ospreys head coach Toby Booth says he is unsure whether Wales fly-half Gareth Anscombe will return before the end of the season from a serious knee injury.
Anscombe has not featured since suffering the problem while playing for Wales against England in August 2019 at Twickenham.
The 29-year-old posted pictures on social media of him running this week but has not returned to full training.
"He's still in the rehab phase and isn't involved with us," said Booth.
"I don't know if I'm honest when he'll be back... there is nothing on the very near horizon of him being involved.
"We take the nature of his injury on a weekly basis. We'll keep looking into it, keep building it up and see where it takes us.
"It's governed by how he responds to training and how he feels about it.
"With the nature of that sort of injury you're going to have to put together a few weeks of training because, irrespective of the injury, you need to build up some resistance to injury and fatigue. So there are many things at play."
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The new Rainbow Cup starts this weekend, with the final due to be held on 19 June, and Ospreys begin their campaign against Cardiff Blues on Saturday at the Liberty Stadium.
It was announced this week that the European teams would be not facing South African sides as planned because of Covid-19 restrictions.
"It was disappointing because you want fresh challenges," said Booth.
"It's new ground for all of us, especially when it changes on a daily basis. It's the same old faces under a different umbrella.
"We're excited about playing and will strike a balance between people who deserve an opportunity and continuing our momentum."
Booth also confirmed Wales second-row Bradley Davies is ready to return to action after suffering a shoulder injury against Munster in November 2020.
Scrum-half Rhys Webb is also recovering from a shoulder injury and could recover before the end of the Rainbow Cup.
Centre Scott Williams is back in light training after picking up his own shoulder problem in the 17-3 victory at the Cardiff City Stadium on New Year's Day.
Williams is out of contract at the end of the season after three years at the region since signing from Scarlets.
Booth welcomed the news Wales captain Alun Wyn Jones has signed a one-year extension with Ospreys and the Welsh Rugby Union until the summer of 2022.
Jones is the world's most capped player with 157 international appearances and will be 36 in September.
"He's an incredible player, an icon of Welsh rugby, and at his home region," said Booth.
"It speaks volumes for what he and we want to do on and off the pitch, so I'm delighted about that."
"If people feel his performance is declining, then you should watch the Six Nations.
"Things are governed by what he delivers and Alun Wyn would be the first to say that. He's delivering elite performance week in, week out."