That was partly because it was not the first time the suggestion had been made since he started telling people he was committing himself to Glasgow Warriors for the rest of his career, but also because retirement is a long way from his thoughts right now.
"That is absolutely not something I am thinking about," said the 31-year-old, who has been club captain since he returned to his home city six years ago.
"I was speaking to Gregor [Townsend, Glasgow's head coach] last night because a friend of mine had said the same thing and I didn't realise that saying I was planning to finish my career with Glasgow might be seen that way. I'm really enjoying my rugby right now and I believe that the next two or three years can be some of the best of my career."
He did admit, however, to being increasingly aware, as he moves deeper into his thirties, of the need to look after himself and credits Stuart Yule, Glasgow's strength and conditioning specialist, with coming up with programmes that are allowing him to do so.
However, he only need look to the example of the two international locks with whom he started his career at Edinburgh for inspiration, since Nathan Hines and Scott Murray, the owners of a combined 164 caps, are both in their 37th year, yet still performing mightily.
"There's Wagga [Hines] and Scotty both over in France and going well and the way they've done it is by freshening things up by moving," he observed. "However, you can also look at someone like Ian Gough, who started his career at the Dragons but stayed in Wales and has now spent a long time at the Ospreys and is still playing at top level."
That is that established, then. The decision was nothing to do with distant thoughts of retirement. So why make this declaration of intent now?
He is not admitting as much directly, but the timing of Kellock's declaration of commitment to the cause was a similar and arguably even more emphatic statement of what playing for Glasgow means to him to Greig Laidlaw's decision this week to try to get across to his players how much they must care. Along with Nick De Luca, the Edinburgh captain asked their management if he could present to their team-mates what they believe will be required this week to end a sequence that has seen Glasgow lift the 1872 Challenge Cup in each of the last three seasons.
The closeness of the rivalry is demonstrated in the fact that only once in that period have Glasgow managed to win both games and no-one is more keenly aware of it than Kellock, who suffered one of the most uncomfortable days of his career as part of an Edinburgh team thrashed 46-6 at Firhill.
"This is always a big week, regardless of where the teams are sitting, but we had a good start to the season, whereas Edinburgh will be thinking they can get themselves into play-off contention if they win both matches," Glasgow's captain observed.
"There are all sorts of motivational factors. As well as looking for league points the fact that Edinburgh have not won the 1872 Challenge Cup for four years is a major one, so we have to have the same energy going in and we obviously will."
Kellock's message was reinforced by Ryan Grant, another of the hardy band who have represented both Scottish clubs. Very much a peripheral figure when in the capital, his career has been transformed by his move along the M8, to the extent that he is now being talked about as a serious contender for a place in next year's British & Irish Lions squad.
Grant largely missed out on the derbies last year, suffering a leg injury 10 minutes into the first, which ruled him out of the return, but it was his performances in the second half of last season that propelled him into the Scotland team.
"I can't wait," he said. "It's the biggest game of the year for us as a club. These two games could catapult us back up into the top four and last year we put together a good string of wins during the Six Nations which saw us finish in the top four.
"There's that huge rivalry, a lot more emotion in this game, but there's also league points at stake."