And, after an agonising wait, the Men of Gwent have had their worst fears confirmed. The Dragons are pursuing a second opinion but are resigned to losing Harries for a substantial period of time.
The injury has also dashed any hopes Harries had of being involved in the World Cup in September.
"We are unlikely to see him before the New Year. He's ruptured his knee ligaments and, though he's having a second opinion, it's a serious injury," Dragons coach Darren Edwards told the South Wales Argus.
"It's a huge blow for Will and for us. It will affect our recruitment now. Our firepower is diminishing so we've got to have a look at things."
The news completes a double blow for the Dragons, who lost to Edinburgh at the weekend while the Scarlets beat Glasgow to end their hopes of qualifying for the Heineken Cup.
"We didn't play as well as the week before," admitted Edwards.
"We made a poor start when we were off the pace, we lacked cohesion and physicality. We had no complaints.
"The biggest plus point was that we walked off with no new injuries, though Gavin Thomas missed the match with a knee injury.
"Andrew Coombs was our best player and Aled Brew broke the try- scoring record. He scored a really good try after a nice break by Jason Tovey. He's had a fantastic season."
Edwards rung the changes for the Murrayfield clash and defended the decision after critics suggested it backfired in the loss in the Scottish capital.
"It's important to give players a chance - we've got to develop players. It's invaluable exposing them because the more they get up to that standard the better we will do.
"We've got a whole summer to work on things now."
But the Dragons will have the perfect opportunity to make amends with another huge Welsh derby, against Cardiff Blues, at Rodney Parade this Friday.
While the hosts now have no chance of reaching the Play-Offs, the Blues know a bonus-point win will secure their place in the top four.
The Dragons then finish their season against another Play-Off chasing side when they welcome Ulster to Rodney Parade on May 6.
"It's disappointing we're not playing in the Heineken Cup, but you get what you deserve, we didn't score enough points in the League. Credit to the Scarlets for winning in Glasgow, although it would have been nice to take it right to the wire.
"But we've still got two big games to go at home and it's important to finish the season well.
"We will be going flat out and we will put the best possible teams on the pitch. It's the way to go into the pre-season, two good performances now will help break down the barriers."
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