Faf du Plessis cannot understand Kyle Abbott's decision to turn his back on South Africa and join Hampshire, in a move the Proteas captain described as a "red flag" which must be addressed.
Abbott's international career is effectively over after Cricket South Africa (CSA) confirmed the paceman has signed a four-year Kolpak contract, with batsman Rilee Rossouw also moving to Hampshire on a three-year deal.
Stiaan van Zyl, Simon Harmer and Hardus Viljoen had already signed Kolpak deals, while Proteas coach Russell Domingo on Thursday said he has been assured Dane Piedt is going nowhere after the spinner was linked with a move to England.
Du Plessis expressed his concern after losing Abbott and said the trend cannot be allowed to continue after his side secured a third consecutive Test series victory with a crushing 282-run win over Sri Lanka on day four at Newlands.
The South Africa captain said: "It's a red flag. We have to address it. As the Proteas and as CSA, we need to make sure it doesn't happen. It is always going to be a challenge.
"The foreign currency is something that will always be there. It's too important and too valuable to say that whatever happens, happens and there will be players to fill the gap. That's not good enough.
"Opportunity, money, transformation. There are a lot of factors guys will look at as their excuse or as their reason. What Kyle's is, I am not sure. Every single reason is a concern.
"He is someone who has not been sure for a period of time. He wants security.
"I want him playing for South Africa. He is not going to be part of our team so if he is not going to be part of our team, it's time to move on. I respect his decision but I don't agree with it.
"Six months ago, I could have understood it more. Sitting here today, I don't understand it as well. I am extremely surprised.
"I care so much about him that I want him to play for South Africa, I want him to do well and perform on the biggest stage in the world because I think he is an amazing cricketer and that's the place to be. I am disappointed for those reasons."
The uncapped Duanne Olivier has replaced Abbott in the squad for the third Test at the Wanderers, where South Africa will look to seal a 3-0 whitewash.