The Irish international prop is facing a race against time to recover from a hand injury suffered in the Six Nations Championship clash with Italy in February.
"I had the plaster cast off 10 days ago and there has been a dramatic improvement but right now it is only 50-50," said Corrigan.
"However, the team is the important thing and training has been going really well. We're delighted with the ways are going in that department.
"Our international players have been through the mill in the Six Nations but what I have noticed about them in the last few days is the huge improvement since they left the hotel syndrome' they were in with the national side.
"Now they are back home, sleeping in their own beds and eating home food and they are looking pretty happy with that situation.
"We did have a training session against Ulster at the weekend and, although we were missing a lot of those international players, it was an invaluable chance to run through some moves and patterns. It was most constructive, productive and worthwhile - but the real test comes on Saturday."
French champions Biarritz are keen to play the underdog card but Corrigan is adamant that the French club "represent a massive challenge for Leinster.
"We have not been together for quite some time while they have been playing in the French Championship.
" Biarritz are a very strong and experienced side. Their pack is vastly experienced and is rather old fashioned in that they try to wear opponents down up front.
"They also have very nippy and talented backs that can do plenty of damage and their back three are probably their biggest overall threat. We will have to watch them very carefully indeed."
Players like full back Nicholas Brusque and wings Philippe Bernat-Salles, Philippe Bidabe and Australian Marc Stcherbina have potent attacking potential and it could be a thriller in front of a likely 47,000-strong crowd.
"When we were first given the opportunity to decide between Donnybrook and Lansdowne Road it was a matter of doing whatever maximised our home advantage," said Corrigan.
"And playing in front of that sort of crowd at Lansdowne Road is massive. We wanted all the Leinster supporters who wanted to see the match to be able to come to the game and the response has been phenomenal.
"That response has to be a factor - hopefully it will boost us and perhaps intimidate them to a certain extent. That said, they are not short of experience at the highest level, many of them have seen it all before and they have nothing to lose.
"For our part, we will have that support but we still have to perform on the day. That support will do nothing if we don't play to our full potential. We have to give those loyal supporters something to cheer about early on - something to get their teeth into and raise the passions.