However the 23-year-old has only played one RaboDirect PRO12 game this season, against Edinburgh on September 7, due to an ankle ligament injury.
Halfpenny is back in contention to start against Glasgow Warriors on Saturday and Davies is in no doubt as to quite what a difference the Welsh international could make.
However while he welcomes his return the Cardiff boss has been just as quick to praise the efforts of his replacements Dan Fish and Tom Williams' in the No. 15 jersey.
"Leigh has passed fit, so he's going to be available and potentially playing," said Blues boss Phil Davies. "It's great to have him back. Arguably for me, he's one of the top two full-backs in the world and to have him playing with us is a great boost.
"I am pleased to get him back. But one thing to stress is the form of Dan Fish and Tom Williams as well. I have been very pleased with the way they have been playing at full-back."
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