And Irishman Kearney knows all about Kirchner's talents, the two full-backs having lined up against each other in the 2009 British & Irish Lions tour to the latter's homeleand.
Kearney has since gone on to become a tour winner with the British & Irish Lions this summer in Australia, but the 27-year-old is not about to take the Leinster 15 jersey for granted in the face of the club's new Springbok recruit.
"We always say competition is a good thing when you're the right side of it," Kearney told the Irish Examiner.
"Maybe when you're in second place, it's not as good! How that is going to pan out over the next few months, I've no idea.
"Even with him now, I know there's going to be good competition, as there has been over the last few months.
"Back-three players are something we've been strong in. It's the same as when Isa Nacewa was here, the dynamics of if we play together or stuff like that hasn't really been laid down yet. There will be some interesting chats in the weeks ahead.
"[Zane's] been pretty quiet so far. It's difficult for him, coming to a new team, to a squad that their season is kicked off and guys are playing and big matches are coming. But he's going good.
"Guys are making an effort and it's important over the next few weeks that guys do make an effort, take him out for some grub and show him around. Little things like that are going to make a big difference to him."