'Gers boss Ally McCoist has so far seen his side perform poorly at the back in their opening pre-season matches against German opposition and is keen to bring in some defensive depth before the Scottish Premier League season kicks off on July 23.
McCoist confirmed that there had been a bid and said he would now wait and see what the Spaniards want to do but he did make it clear that he would more than likely pursue other defenders this summer.
"We have contacted Espanyol with a bid but haven't heard back from them," he said.
"We'll wait and see how things go on Thursday.
"Raul's a centre-back and we definitely need strengthening in that department.
"We just need cover and hopefully Rodriguez will give us that.
"He's someone I'd look to bring right into the team. I'm not looking for players who aren't going to play.
"We're still looking at other players and there will be other bids going in over the next 48 hours.
"Rodriguez won't be the last defender we go for."