Blake has signed a contract to play for Scottish club Edinburgh, while Spence has picked up a deal in France to play for Bordeaux as medical cover.
Blake, a loose forward and former New Zealand Colt, has played 20 games for Otago and Spence, a utility back, has played 39 games in the Otago jersey.
Union general manager Kinley said he had talked to both players and both had indicated they might come back and play for Otago in the ITM Cup next year.
''They are both young guys who want to get away and see a bit of the world. I am not disappointed they have gone,'' he said.
''They might be back. I have spoken to both of them and they have given that indication. You are never going to hold on to every player.
"I believe if they get an opportunity to see the world and earn a bit of money while they are doing that, then there is nothing wrong with that.''
Kinley said he had spoken to Otago players and he did not know of any other player looking to move on.
''We have a lot of players here who are tertiary students and enjoy the environment down here so won't be going far.''
With a new coach yet to be appointed by the union, Kinley said some players were contracted for next season.
''But we do not want to have a new coach coming in and then say to him here is your whole squad for 2015. And that is also going against what we have been trying to do in the past three years, rewarding guys for playing well in club rugby.''
Kinley said the process for selecting the coach was ongoing and was at the interview stage at the moment.
He said the process always took longer than hoped.
But he would rather spend more time and get the right person than rush and not get the right man for the job.
