Celtic released 11 players recently, signalling their intentions to keep things fresh at the club and not rest on their laurels.
Siwelele did finish in the top eight, but their ambitions are to push for the top four bracket next campaign.
"Look, Moses has been at the club for more than 10 years, but he indicated to us that he wanted to retire. He has served the club very well, with distinction and has been one of the longest serving players in the club's history," Larsen tells KickOff.com.
"It was always going to be difficult to part ways with a player who has been at the club for so long, but life goes on and we wish him the very best and hopefully we will be able to get players of Moses' calibre to replace him and take the club forward."
Larsen says he has switched his focus to the younger generation.
"Auguston is an up-and-coming youngster; he has played at the Under-20 and Under-23 international level. We rate him very highly and we are sure he will make a huge impact at the club this season as we have great expectations of him," Larsen says.
The focus for Larsen and his team in the near future is to improve their form away from home and to make their home matches incredibly difficult for opponents.
"Two seasons ago we finished on 52 points and this past season we were plus minus 10 points shy of that mark. We fell a bit short," Larsen explains.
"It was mainly due to the fact that we were not good enough on the road and also were not as strong at home like we were two seasons ago when we lost only one match at home."
Meanwhile, Celtic will welcome winger Lyle Lakay to their pre-season training camp with a view to signing him.
Lakay has been on loan at First Division side FC Cape Town, but he belongs to SuperSport United.
Larsen will have a good look at Lakay during pre-season and if he likes him, then it will be up to Celtic and SuperSport to discuss a deal and agree on a fee.
If a move does not happen then Lakay is expected to return to SuperSport.