After the match, Foley said: "At the moment, he is in there with ice on (his leg). In the next 24 to 48 hours we'll know more."
Munster travel to the Liberty Stadium on Friday as they bid to defend their crown but O'Connell was forced to use crutches having left the field and will be a doubt for that match.
On the night, Munster were emphatic and racked up five tries through Tommy O'Donnell, Stephen Archer, Mike Sherry, Peter O'Mahony and Simon Zebo all crossed to give Tony McGahan a fine send off in his last match in charge at Thomond Park.
Iain Henderson, who has impressed for Ireland Under-20s this season, grabbed Ulster's only try of the match as Brian McLaughlin rested a number of players in preparation for their Heineken Cup final clash with Leinster.