A shattered Coates limped off AAMI Park on Saturday night after attempting to dive to the ball and had to be assisted to the change-rooms by trainers.
The injury, his second hamstring issue of the season, threatens his participation in the third Origin match in Brisbane on July 17.
Xavier Coates suffers his injury attempting to score. (Joel Carrett/AAP PHOTOS)
Melbourne coach Craig Bellamy said Coates would undergo scans but admitted it didn't look good for the 23-year-old.
"Obviously it's not great, you know, he's had a few issues," Bellamy said.
"Until he actually gets a scan, we won't know the exact extent of the injury but I don't think it's too good.
"I wouldn't think that he'd be available (for Origin) but I don't think the medical staff are going to sort of make that prediction until they see a scan either."
While Coates backed up from Wednesday's Origin II, played next door at the MCG, Melbourne skipper Harry Grant was rested while star fullback Ryan Papenhuzen was also missing with a foot injury.
With injured Cameron Munster already sidelined, the Storm struggled to turn a glut of possession in the first half into points.
The Raiders however deserved credit for their defensive effort, particularly after giving up 82 points in their past two losses.
Canberra ended up making 345 tackles to the Storm's 223, with five ruck infringements by the visitors in the first half alone.
It took until the 36th minute for Melbourne to break through for a 6-0 lead with prop Josh King finding a hole left by Canberra skipper Elliott Whitehead running out of the defensive line.
After a number of first-half errors Canberra fullback Kaeo Weekes made amends with a brilliant 90-metre dash one minute into the second half to draw level with the NRL ladder leaders at 6-6.
But Melbourne again hit the front with dummy half Bronson Garlick finding Shawn Blore who went over four minutes later.
That margin was pushed out to 10 points when promising young centre Jack Howarth crashed over for his first NRL try in the 51st minute.
Storm teammates congratulate Jack Howarth (c) after he scored his maiden NRL try. (Joel Carrett/AAP PHOTOS)
Coates looked to have sealed the match but the video referee ruled a knock-on, giving the Raiders hope of closing the gap.
However going down to 15 men, after losing debutant Jordan Martin, Ati Mariota and Jordan Rapana to head knocks, made the formidable task even more difficult.
Canberra coach Ricky Stuart was pleased with his side's reaction after the recent heavy losses and described it as their "best defensive display this year" but said they gave the Storm too much ball.
"If you have a look at how many tackles we had to make to their tackles, it was nearly double," Stuart said.
"You can't just keep turning over that much football, we just made it too hard for ourselves."
Stuart questioned some of the refereeing and bunker decisions, particularly the multiple six-again ruck calls which took a toll on his team.
"We were on the wrong side of the guessing game again," he said.
"They're just guessing, those six-agains, they just guess.
"I give one away here, one away there."
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