Leavy (hamstring) and Nacewa (calf) have shrugged off their knocks, while Scott Fardy is likely to get the nod once more in the back-row.
It’s been a remarkable journey for the 26-year-old, who was appearing for former Wales coach Mike Ruddock’s Dublin club side Lansdowne after failing to make the cut with Leinster.
Playing for Argentina from 2004-2015, Juan Martin Fernandez Lobbe captained his country and earned 71 caps.