Keith Fahey, Morgaro Gomis, Steven Caldwell, Pablo Ibanez and Adam Rooney
have not been retained by the Blues boss as he seeks to rebuild his squad ahead of next season's Championship campaign.
All four of their contracts were due to finish next month, although in Caldwell's and Fahey's cases the club had one and two-year options on them respectively, which Clark chose not to activate for financial reasons.
"I have pre-warned everybody the last few days that the club is having to go down a completely different route," said Clark.
"Keith is on a contract from the club's Premier League days and obviously we can't continue to do that kind of thing again. The level of contract we could have offered Keith would have meant not just a minor drop in salary, but a huge drop. So there's the financial scenario, and it's a very tough one - as it was with all of the other players.
"Certainly with Keith, he showed in the two games he played in when he came back from Ireland, at Middlesbrough and at Crystal Palace, that he's a class act. But on top of that he's had one or two injury problems this season and as I found out to my cost when I took a little gamble on Stephen Carr it backfired and then there wasn't much left in the kitty to try and get a replacement.
“There’s no doubting Keith's ability. He is an extremely talented player. But the reasons were mainly financial and a little bit the injuries he has had since I've been here. He’s not injured now, he's fit, but I have to take everything into careful consideration as we try to move on as a football club, in changing circumstances. Keith has been brilliant.
“He took it really well when we had a chat. He knew the situation we are in and was very philosophical. I would like to thank him for what he has done for this football club and wish him all the very best in the future.
"The same goes to the others - Steven Caldwell, Morgaro Gomis, Pablo Ibanez and Adam Rooney
. As I've said, as a club we are going down a different route. As the manager, it's never easy to break this kind of news to players but that's football. It's my job, I am determined to build a squad here that can hopefully bring us success and I also have to manage the expectations of everything at the same time."
On the flip side Paul Robinson, Jonathan Spector, Wade Elliott, Colin Doyle and Akwasi Asante have all been offered new deals.
"It's totally merited, the offer of a new contract to Paul," added Clark.
"He has been fantastic, both on and off the field. He has been a great example to the younger players, with his experience and the way he conducts himself. But most importantly, his performances warranted the offer. He may be of an older age, but he's still very fit, he doesn't miss training. And, in fact, we have to try and get him to rest some days.
"Wade, he's been another of those players who has done extremely well for us this season. I think he has responded to the younger lads around him. His performances have been very consistent, you know what you are getting from him, and he has scored some important goals too.
"Jonathan is another player who has the experience, ability, and he can cover many, many positions as well."