Not only did he fail to win a place in the Scotland starting team but Kellock had to suffer the humiliation of being usurped by a journeyman player from New Zealand, Matt Mustchin who looked more comfortable playing in the third rather than the second row of the scrum.
When everyone was fit and available Hadden tended to go for size over skill by selecting both Nathan Hines and Jim Hamilton. When those two were unavailable the former coach picked Scott MacLeod to partner Mustchin in the boiler house which is what happened when Scotland last toured Argentina. Kellock was so far down the food chain that he was effectively fish bait; not any longer.
He is not the type to gloat but the man asked to lead Scotland onto the field for the first time ever allowed just a flicker of a smile to ghost across his features when he was reminded of his previous difficulties.
"It happens with everyone, it's not just me," said the new team captain. "I haven't changed much, I worked really hard previous to this year as well, trying to make sure I played as well as I could but that's just the way sport is. Coaches have the final say and all you can do is try and force your way into the reckoning by playing well and working hard.
"The opportunity to play for Scotland kept me going and the fact that I love playing rugby kept me going. Glasgow being, day in and day out, a great place to play rugby kept me going.
"You do get down, there is no doubt about that, but if you start feeling sorry for yourself or if you look elsewhere and blame other people or other things then you are not going to get back in (the team]. When you are not selected you have got to listen to the feedback, you've got to deal with it, you've got to make sure that you improve the bits you need to improve."
The question in Kellock's case is whether he has really improved significantly over the last 18 months or whether it is simply a case of someone who was already a good player responding in a positive way to the support and belief invested in him by a new management team.
Kellock for one believes in the latter. "I don't really feel like I've been doing anything hugely different," he replies when the question is put to him.
"Looking back on the season my performances have been a lot more consistent. It's not a switch I've had to press, it's just happened, I've really enjoyed working under Sean (Lineen] and Shade (Munro] at Glasgow. I thrive on being captain, I think it adds to my game.
"Similarly with Andy (Robinson], he's very clear with what he wants from me, I speak to him regularly, he concentrates on your strengths and that's just helped me throughout the season."
Kellock has now been Glasgow skipper for four seasons which, for the large part, have been reasonably successful ones. He is obviously one of those characters who thrive on responsibility but the whole leadership aspect can be over-played. It is a point made by Robinson who had this to say about his new skipper.
"I expect Al to lead from the front, as he has done in his performances this year for Scotland. He has to focus on his game. We have enough leaders on the pitch to give the team direction. Al has to fit into his role as a lock forward."
In other words when Scotland face a powerful Pumas pack tomorrow Robinson needs his big men throwing their weight about rather than composing Churchillian speeches in their head. If Kellock can repeat his Dublin performance where, along with Hamilton his second row partner, the pair somehow poached seven Irish throws at the lineout, then Scotland will already be half way towards beating Argentina who like to dominate territory and squeeze the opposition into making mistakes.
Hines and Hamilton were simply too similar to yolk together in the second row and that much has been proved beyond all reasonable doubt by Kellock's form for Scotland over the season. If he had done nothing else, the former Allan Glens player would be worth his place for the improvement he has brought to Scotland's work at the restarts although it could hardly have got very much worse. So is he now comfortable with his place in the team?
"I never get comfortable," said Kellock. "I've said it before, I've been in and out a little bit in years gone by and you can never get comfortable and feel as if you have cemented your place. You have to work hard at training, you don't know who is going to be playing until it's named. It's very fragile isn't it. One bad performance and you might not be playing."