Ireland head coach Joe Schmidt will hope to have the Munster flyer available to him for the 2014 Six Nations but Zebo has made just three appearances in the RaboDirect PRO12 this season.
But with Munster riding high at the top of the RaboDirect PRO12 table, Penney admits there is no need to risk Zebo before he is ready.
"I think he'll be back [training] on the grass this week," Penney told the Irish Examiner.
"Obviously because of the nature of his injury we'll just be ultra cautious.
"We've got some good boys going in the back three, if he's not right, he's not right.
"We don't need to try to force him because he's really important to Irish rugby. He's probably been shut out at the moment so he just needs to come back and be in good form and try to force his claims."
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