Murray made his first appearance of the season with a 27-minute cameo off the bench for Penney’s men in the 19-15 victory over Leinster last weekend.
The 24-year-old was given an extended break after playing a crucial role in the historic British & Irish Lions’ series win in Australia during the summer.
And while Murray is already an integral part of the Ireland set-up, starting all five of their games in this year’s Six Nations, Penney believes he will only get better.
“Jeez, he looks fantastic doesn’t he? How good is that kid?,” Penney told the Irish Examiner.
“He can be the best in the world, if he’s not already, he’s not that far away. He’s a bit of a genius.
“Coming off the back of having no football really, and having a 20-minute cameo like he did, superb.
“If you talk to him it [the Lions tour] was an eye opener for him but the kudos he got for running ahead of a couple of guys (Mike Phillips and Ben Youngs) with probably higher profiles and doing a great job on that tour against probably the best nine in the world, (Will) Genia.
“I think he did a sterling job with the way he played against him. And I think he knew I noticed how good he is and he ain’t the finished product yet.”
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