The big lock's participation in the squad session fuelled speculation about the exact date of his return to action, but head coach Tony McGahan was non-committal on that particular issue when speaking afterwards.
"It is far too early to say really. It's good to see him back but we'll wait to see how he comes through this and Thursday's session before we'll have an indication of when he'll be ready to resume." he said.
Fellow back Barry Murphy is making good progress with a foot injury and showed well in training, suggesting that he is ready for game-time sooner rather than later.
McGahan will announce his squad for the Harlequins game on Wednesday afternoon, with the squad completing their training on Thursday and the team announcement due on Friday afternoon.
A small number of tickets for the semi-final are still available from the usual outlets. Thomond Park Stadium officials are expecting them to be snapped up quickly.