McCall was club captain of Ulster when they won the competition in 1999, although injury ruled the Irishman out of the final against Colomiers.
Despite his Irish roots, McCall has said that his loyalty is with a Saracens side who are hoping to reach the last four of the Heineken Cup for the first time in their history.
"If you are asking me about the Ulster connection, for me it won't make it any better or worse if we win or lose because it is Ulster, because I have a real attachment with this group of players," McCall told Sky Sports News.
"We have been together for four years now and we have been through a lot over those four years. To get into a semi-final with this group of players would be a great thing."
Saracens were defeated by Clermont Auvergne in the quarter-finals of the Heineken Cup last season.