"We both need our backs for different things," said the reigning European Player of the Year.
The difference is that Kearney is back in harness for Leinster, while O'Connell is on the road to recovery and powerless to affect Munster's Heineken Cup pool matches or, worse again, Ireland's Six Nations campaign.
Kearney had time to dwell on his disc problem.
"It was not ideal. It was a difficult time because there were a couple of months when there was a lot of uncertainty there.
"The difficulty with that is that you feel you are wasting time.
"It was a problem I have had for a few years. I knew I was going to have to have something done with it sooner or later. The timing wasn't ideal this year.
"Touch wood, it is all behind me now. I feel good. It will take time before I am back to 100 per cent. In terms of the recovery, I was really happy.
"It was only ten weeks. At first, I was told 12 to 16. But, the target of coming back for big games in Europe focuses you more."
They don't come any bigger than the next one. Leinster are way off the pace set by Clermont-Auvergne in Pool Five and in need of a minor miracle to qualify as one of the two best runners-up.
The Scarlets are an unpredictable lot. If they come fully intent on causing an upset, they have the artillery to shred the best defences.
However, the facts are that the Welsh club have lost all four matches in the Pool. They have nothing but pride to peddle at The RDS.
Against that, Leinster have been to the well a number of times in the Heineken. Think Harlequins in the 2009 quarter-final. Think 2009 final. Think 2011 final.
"You probably take a little bit of confidence from knowing that you have been in those situations before," said the British and Irish Lions full-back.
The temptation is there to go after the first of four tries as early as possible. Don't be surprised to see Jonathan Sexton hoof a kickable penalty into the corner.
"I can't stress enough how, as a player, you have to leave that whole aspect behind you and focus on the 80 minutes of rugby.
"We understand the dynamics of the situation we are in. But, if you lose sight of the game and what is immediately in front of you, your focus starts to drift.
"That is the one area where we have to be clever and sure that it doesn't happen to us. That is when you are in danger of not performing."
The return of Brian O'Driscoll, Luke Fitzgerald, Isa Nacewa, Richardt Strauss and Kearney has added weight to the argument that Leinster can overcome their recent failings against Clermont.
"Regardless of the calibre of player coming back, there is freshness and energy. That has brought a lot to us as well. It is just having bodies and voices back on the field that you might not be used to.
"To win these competitions, you have to go through some tough moments. This is our tough moment. It is going to test us.
"Hopefully, we'll come out the right end of it."