Elwood has confirmed that lock Michael Swift will not be available for the trip and will target a return to action against Edinburgh next month instead.
But in terms of McCarthy, who started all of Ireland's Six Nations matches, Elwood is hopeful that the second row will shrug of a knee injury in time for Saturday's clash.
Connacht are currently 11 points behind Munster but victory would keep alive their hopes of catching their rivals, and Elwood hopes McCarthy, who will join Leinster at the end of the season, plays a big part in their run-in.
"We have given Macca a few days off post-Six Nations. We are going to see him on Thursday and we'll assess his injuries, he has been carrying a couple of knocks, so we gave him four days off," Elwood told the Irish Independent.
"It would be nice for us, as Macca is a very good player and he is very important for us. He has got five games left in his Connacht career and we have a lot to play for in those five games.
"But he has been through a tough campaign in the Six Nations and picked up a few knocks and we'll assess him on Thursday.
"He is just returning from his knee injury so that's the big concern, but hopefully his knee is okay because he was substituted the other day."