Lydiate looks certain to miss to autumn internationals against Argentina, Samoa, New Zealand and Australia and is likely to be out for the rest of the season.
Lydiate's impressive performances for his country in last year's RBS 6 Nations were the cornerstone of their Grand Slam triumph.
But with the Salford-born star set to go under the knife on Sunday his club coach Darren Edwards admits his international hopes for this term appear to be over.
"It's a huge blow for him and for us," he said. "I don't know the time scale yet or how long he will be out. Let's just hope he still has a chance to achieve his goals.
"Dan is a world-class player whose tackling is known all over the world. He's also a great guy to have around the environment and is a good influence on everyone around him. It will be very sad not to have that presence."