The 21-year-old Perth-born utility has been playing through pain for the last few weeks at Boro, having missed two months earlier in the year due to the pelvic problem.

Middlesbrough boss Gordon Strachan told the club's official website: "Our medical staff have to get together with Australia's medical staff and say, 'This is the condition he's in' and then decide what happens."

Those talks are expected to take place before Australia boss Pim Verbeek makes the final call on his Socceroos squad for the South Africa tournament.

Williams told ComeOnBoro.com last week: "It feels like it's going to snap everytime I run. I'm not really training. I'm getting through games with injections, it's not ideal but I'm getting through it."

Strachan revealed he wouldn't risk Williams in Boro's final Championship game of the season against Leicester City on Sunday.

"We've got to protect a really good player," he said. "He's been getting better towards the end of games when he realises the pain won't be there much longer."

Since arriving at the Riverside in October, the Boro boss has been impressed with Williams, even offering the young Aussie a three-and-a-half-year contract extension in February.

Strachan added: "There's no limit to what he can achieve."

Williams' Boro and Australia teammate Scott McDonald told SkySports: "I don't know what the script will be for Rhys, there's a bit of a worry there. But hopefully he can now rest up and find full fitness.

"It would be great for the club to have three boys representing the one nation."