However with Munster's hopes of a RaboDirect PRO12 play-off place receding after last week's draw with the Ospreys, O'Connell's return could prove a major boost.
He is set to line up for Munster A against their Leinster counterparts on Tuesday and will be keen to prove his fitness ahead of the Heineken Cup quarter-final against Harlequins.
In his absence Munster have struggled for consistency, but Penney insists the commitment is there despite the fact they have not won any of their last three games.
"There was no lack of commitment and that was important," said Penney after the draw with the Ospreys last weekend. "We could easily have picked up a couple of penalties.
"I don't think it was a lack of effort. It is difficult when you have got the opposition players in your backline when you are trying to play and the officials probably let a few things slip through there.
"So, maybe, on reflection, we were not always in control, but we created opportunities, and in tight games you need the odd thing going for you and that wasn't for us."