Centre Newman has not played since suffering the serious injury against Hull KR in September but coach Richard Agar hoped he would be able to resume against St Helens on June 11
However, Super League's reigning Young Player of the Year had a scan on the injury earlier this week and has been told it could now be early July before his return.
Agar admitted: “It is frustrating for him.
“We were all systems go. But it is such an injury that if the injury is not healed properly and it goes again then we have got major problems.
“It’s not like it wasn’t a major problem anyway. But I’m talking major, major problems that could put question marks on his career.
“We said all along that we were going to take this (slowly).
“He’s such a brilliant talent. He’s working so hard and he’s so young with so much of his career in front of him…
“The speeding of the healing probably just hasn't gone as it did early doors. It healed really well really quickly and has now just tapered off a little bit.”
Agar insists the 21-year-old will bounce back.
“Harry had a bit of a setback and disappointment but that’s purely in time,” he said.
“ It’s not that there’s any complications with the injury. Absolutely not. It’s just the speed in which the bone is healing and knitting together.
“The next scan is in about six weeks so we’ll have to wait for another six weeks rather than the three we are at the moment.
“It’s such a big traumatic injury but we always said for Harry it’s the bigger picture - the ten years he has after this.”
Meanwhile, Leeds had hoped to recruit Williams, the ex-Wigan Warriors stand-off who was surprisingly given an early release from his contract by Canberra Raiders this week.
He had been looking to secure a release at the end of the season to move back to the UK for personal reasons but the NRL club’s shock move has caused a flurry of activity for the gifted 26-year-old’s services.
Leeds stand-off Robert Lui is retiring at the end of the season and they have already seen fellow half-back Eastmond retire earlier this month so they are searching for a playmaker for 2022.
But Agar says it looks like no deal for Williams will be done - and it now appears a return to Wigan is most likely or another club on that side of the Pennines.
“I’m really good mates with George’s dad Pete,” he said.
“He’s a close friend of mine. We did speak to George’s agents.
“The homesickness stuff is very real and with a baby on way it’s fair to say and established that George wants to live back in his own sort of area.
“We seriously did inquire but the fact he wants to settle back in the north-west - I’m not divulging too many secrets there - we think that pretty much rules us out of signing him long-term.
“We got the feedback that it’s certainly not the club or anything like that but he simply wants to be settled in the north-west so I would suggest that would rule us out.
“Things do change but at this stage it’s unrealistic we’re going to be in the running.”