Rufus, who was taken off with an ankle injury on Saturday, is likely to be out for some months and Paul admits: "It is a huge blow, and with the squad we are running at the moment any injury is a massive knock to us.
"There is no natural left back. Shaun Byrne has filled in but there is not a lot of cover, as elsewhere in the side.
"It is a specialised position, something we are looking at and Glenn is working hard at sorting it out.
"I would think it might be soon, but the list is not massively long that we have drawn up and for each person on the list there could be a different reason for it not to happen.
"But Shaun has filled in there in pre-season and he would like to have another crack at it.
"The introduction of Rufus and Glen Johnson was paramount in our resurgence as a defensive unit last year and it is important we pick someone to carry on those defensive qualities well.
"It is a blow but we just have to pick ourselves up and deal with it, with fingers crossed that we can do something soon.
"We have got to get a bigger squad because the games are coming in fast and furious - we need players.
"We hope that nothing else happens and that the injured players that are out return quickly."
As for the draw against Sheffield United at the weekend, Paul says: "Saturday was frustrating and on another day it would have been different; we are short on variations in terms of players to break things down and it was a bit of a stalemate with David James not having a lot to do."