O'Donnell was a late draft onto the Munster bench for the Treviso game when Donncha O'Callaghan was re-routed to the CUH where his wife gave birth to their second child.
And in London on Saturday, John Ryan had his first experience of English Premiership when he came on as a replacement for London Irish in their opening League game at the Madejski Stadium.
Ryan who is on a short term loan with Irish won't have fond memories of his debut as his side went down to Gloucester, a defeat that sees them last but one in the Premiership table.
Meanwhile in Cork today Rob Penney begins preparation for the Round Three RaboDirect PRO12 trip to Ravenhill (Friday).
Penney's choices will be broadened with the availability of some of his international contingent although also he also has the consideration of the A Interprovincial that takes place earlier in the day in Belfast.