Andrew Hall says Cricket South Africa (CSA) must let young players know how highly they are regarded to prevent the cream of the crop from signing Kolpak deals.

The Proteas were rocked last month when seamer Duanne Olivier turned his back on his country to sign a three-year deal with Yorkshire.

Kyle Abbott and Rilee Rossouw are among the other South Africa internationals who have signed Kolpak deals, while Morne Morkel joined Surrey after ending his Proteas career.

Former South Africa all-rounder Hall expects more to follow, but wants CSA to do everything in its powers to stop promising talent from slipping through the net.

He told Omnisport: "It's a tough one. It's more prevelant to the younger players who are coming through the system. 

"Cricket South Africa must earmark players and have open, honest conversations with them to let them know they have been identified and are being watched.

"They must be encouraged to keep playing and earn a place. There are times when you can't get into the side because of the players who are already established.

"I think back to having to compete with Jacques Kallis, Shaun Pollock and Lance Klusener - three world-class all-rounders - so it was difficult to get into that side and you have to keep working at it.

"But I was spoken to by the people in charge and told I was next in line. It gives you reassurances and that must happen now as the young players coming through are the ones, on the whole, who are going to be targeted."

Hall can understand why Olivier opted to ply his trade in county cricket.

He said of the 26-year-old's move to Headingley: "I would imagine that contract would have been signed last year, I don't think it's the type of thing that at the back end of him doing exceptionally well in the Tests, he'd say 'I'm just going to go and sign a Kolpak deal'.

"I think it was done prior to him having this good run of form where he's played in the system in South Africa [and] done well, he felt he's not going to get given a long run in Test cricket so because of that he signed a Kolpak deal.

"He's got to think of his future and we all know you only get a limited amount of time, so in his position he'll know he will be well looked after at Yorkshire.

"He could end up being there for the next five or 10 years. It's a catch 22 situation for him, but I would imagine with the money being talked of that he was offered, he would not make that in international cricket."