Second placed Ballymena travel to Dublin to play St Mary's while third placed Lansdowne may be able to spring their Leinster lions, Gordon D'Arcy and Aiden McCullen from the bench, if needs must at home to Co Carlow.
Blackrock are another side who will have their mettle seriously tested this afternoon. They take on a Cork Constitution outfit that will include, Brian O'Meara, Jim Williams, Mick O'Driscoll and Donncha O'Callaghan, in Temple Hill, in what is a must-win game for Con who lie fourth from bottom of the table.
AIB League Division One. Belfast Harlequins v Buccaneers, Deramore Park - Alain Rolland.Clontarf v Clontarf v Garryowen, Castle Avenue - Simon McDowell.Cork Constitution v Blackrock College, Temple Hill - David Keane.Dungannon v Terenure College, Stevenson Park - Colin Stanley.