O'Callaghan made his first start for Munster in August 1998 against Edinburgh Reivers at Musgrave Park and the 34-year-old, who signed a two-year contract extension just before Christmas, is showing no signs of slowing down according to Penney.
"It's a great achievement for Donncha. One great man (O'Gara) being replaced by another great man in the record books, which is what happens. Donncha deserves every plaudit and superlative that you can dish out to him," he said.
"He's been such a great professional for such a long time and he still has a lot left in the tank yet.
"He's a pretty special athlete and he has a great mentality. I can't speak highly enough about the man and his commitment to Munster."
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