However, Ruddock has tipped his skipper to make a successful return when he is fully recovered and also backed Greg Rawlinson to continue to lead by example in his absence.
"Pat has had a setback with his injury. He's ended up having to have some blood drained out of his leg and go to hospital," said Ruddock.
"There's quite a lot of blood under the muscle that has congealed and needed to be drained off. He has also had a bit of a reaction to some painkillers.
"But he's a tough guy if anyone is going to make a rapid recovery after something like that it's going to be Pat Sanderson. We wish him all the best wishes in terms of getting himself right but it's probably be going to be a number of weeks before he returns to action."
With Pat unable to to take up his role as captain, Ruddock confirmed that lock Rawlinson would continue to lead the side at Adams Park.
"Greg will continue as captain in Pat's absence," added Ruddock. "In terms of Pat we're not going to give any deadlines at this stage, we're not going to put any pressure on him at all.
"All we know with Pat is whenever he's going to be fit will probably be three weeks before any other mortal would of made it.
"We shall support him now and get him fit and healthy again. When he's healthy we'll pick him, but in the meantime Greg will continue as captain.
"It was a tough start for him but he is a 100 percent guy and a genuine guy, he's got the respect of everyone here and wants to get things right. Greg is the man who wants to take us forward at the weekend."