Optimism that Mafi will escape sanction was low in Munster circles and Earls' return to contention is therefore extremely opprotune.
The Ireland international, who is working his way back from groin and ankle injuries, took a full part in the session at UL and showed no ill-effects afterwards.
Speaking at Monday's Irish launch of the Heineken Cup, Munster coach Tony McGahan said: "We would hope that Keith is available for selection this week.
"He did a little bit (of training) last week and he is back again this week. He was very nearly right before he did his ankle a few weeks ago, he was absolutely flying it.
"That set him back a bit but he should be right to go hopefully."
The Australian will confirm his team and replacements to face London Irish on Friday afternoon.
Prop Tony Buckley is expected to be fit for selection after missing the defeat to Leinster with a stomach bug, hooker Jerry Flannery is close to returning 'in the next week or two', while injured captain Paul O'Connell is confident of playing again before Christmas.
MUNSTER Squad (v London Irish) - Backs (13): Tomas O'Leary, Duncan Williams, Peter Stringer, Ronan O'Gara, Scott Deasy, Paul Warwick, Danny Barnes, Keith Earls, Lifemi Mafi, Johne Murphy, Sam Tuitupou, Doug Howlett, Denis Hurley.
Forwards (17): Wian du Preez, Marcus Horan, Mike Sherry, Damien Varley, John Hayes, Darragh Hurley, Tony Buckley, Billy Holland, Donnacha Ryan, Donncha O'Callaghan, Mick O'Driscoll, Alan Quinlan, David Wallace, Niall Ronan, Denis Leamy, Peter O'Mahony, James Coughlan.