Cape Town - Former team-mate Mark Boucher says Jacques Kallis is "probably the best cricketer that's ever lived in South Africa".
Kallis's Test career will come to an end on Monday after the conclusion of the final Test against India in Durban.
He scored 115 in South Africa's first innings in what could be his last innings in the longer format of the game.
Boucher said his friend's decision to stop now should be respected.
"When you start asking if you're still enjoying it, or when the enthusiasm to get up every morning is not there anymore, then it's time to call it a day," Boucher told the Volksblad website.
"Look, he loves the game, he's been playing for so long and his workload was massive. Nobody can really say he should have kept playing for longer because they don't know what his workload was. I don't think there is any cricketer in the world who had the workload of Jacques Kallis.
"We're losing probably the greatest cricketer that's ever lived in this country, but when you start questioning things every morning, then you know it's time.
"He is also just human and has been travelling for 20 years now. He deserves his time off to do things at home. He made a lot of sacrifices throughout his career," said Boucher.
Kallis will continue playing one-day cricket for South Africa and hopes to play in the 2015 World Cup in Australia and New Zealand.
The former wicketkeeper also quipped that he and Kallis will now get more time to enjoy playing their favourite past-time, golf.
Kallis's Test career will come to an end on Monday after the conclusion of the final Test against India in Durban.
He scored 115 in South Africa's first innings in what could be his last innings in the longer format of the game.
Boucher said his friend's decision to stop now should be respected.
"When you start asking if you're still enjoying it, or when the enthusiasm to get up every morning is not there anymore, then it's time to call it a day," Boucher told the Volksblad website.
"Look, he loves the game, he's been playing for so long and his workload was massive. Nobody can really say he should have kept playing for longer because they don't know what his workload was. I don't think there is any cricketer in the world who had the workload of Jacques Kallis.
"We're losing probably the greatest cricketer that's ever lived in this country, but when you start questioning things every morning, then you know it's time.
"He is also just human and has been travelling for 20 years now. He deserves his time off to do things at home. He made a lot of sacrifices throughout his career," said Boucher.
Kallis will continue playing one-day cricket for South Africa and hopes to play in the 2015 World Cup in Australia and New Zealand.
The former wicketkeeper also quipped that he and Kallis will now get more time to enjoy playing their favourite past-time, golf.