Marshall will not require surgery but will be out for eight weeks with knee ligament damage suffered in the early moments of Sunday's 24-16 win over St George Illawarra.
It's a bitter blow for the Kiwi Test five-eighth, who was only just embarking on a comeback from a fourth bout of shoulder surgery.
For all the previous setbacks he's had in his six years in the top grade, Marshall told the Nine Network the latest was by far the most devastating.
"This is probably the lowest I've felt, even when I did my shoulders again, this is probably the worst I've felt," he said.
"Sitting in my room alone is probably the hardest part and staring at the ceiling all night and it gets harder every time you keep coming back from things like this.
"I always try and pretend that it doesn't hurt but this time it really does."
Another Kiwi used to seeing the inside of a doctor's surgery, Bulldogs backrower Sonny Bill Williams, will have scans on Wednesday to determine the extent of a knee injury picked up in Saturday night's demoralising loss to Parramatta.
Williams, who has had plenty of trouble with the knee over the years, said the joint was quite painful and swollen.
His absence could open the door for Test winger Jarryd Hayne to make an immediate return to the top grade after he was stood down from the win over the Bulldogs due to his involvement in the incident which led to him being targeted in a Kings Cross drive-by shooting.
Newcastle forward Steve Simpson will have an MRI scan on Thursday, but Knights officials are confident in their prognosis of a grade three medial ligament tear in his knee which is expected to rule him out for 6-8 weeks.