"It's a tough game against them, I've never had an easy one," McCarthy told the club's official website.
"Chris Coleman's teams are hard to beat and hard to play against.
"They have one or two quality players in their team. They'll probably fancy it as they are the home team so I expect a tough game - nothing else.
"If we don't get a result on Saturday then my birthday suddenly becomes a real damp squib.
"Pity it wasn't on a Sunday or Thursday when we weren't playing. But three points would be great and we'll be doing our utmost to get them."