Cape Town - Former Proteas skipper Graeme Smith believes that with the loss of AB de Villiers, the Proteas are facing a challenging period ahead.
De Villiers announced his shocking retirement and cited fatigue, stating that it was the "right time" to call time on his 14-year international cricket career.
Since appearing on the international stage in 2004, De Villiers scored 8 765 runs in 114 Tests with 22 centuries (average 50.66), 9 577 runs in 228 ODIs with 25 centuries and 1 672 runs in 78 T20Is with 10 half-centuries.
Smith, who himself made a shocking retirement at the age of 33 in 2014, believes that the Proteas will never be able to replace the calibre of De Villiers.
"To lose a player like AB, he's irreplaceable," said Smith, as quoted by Reuters.
"There are also quality players there but it's like taking Virat Kohli (India captain) out of the Indian team.
"Everyone will say it's a big loss. More than anything the South African team loses a X-factor player, who can single-handedly win you a game."
De Villiers' decision comes as a massive blow to the Proteas, who would have been counting on him at next year's World Cup in May in England.
Smith reckons that the Proteas will suffer with experience after the 2019 Cricket World Cup in England and Wales.
"I think South African cricket is going to find itself in a very interesting phase in the next year or so," Smith said at the sidelines of the Ceat Cricket Rating awards.
"I don't think the talent pool is quite as good as what it has been for a period of time.
"If a couple of players walk away after the 2019 World Cup, it's going to take a little bit of time for the team to rebuild," he said.
"It's going to be interesting to see players like Hashim (Amla) and Faf (du Plessis) if they play for another year or two after the World Cup. If they don't, it's going to be a challenging period and something South African cricket needs to be aware of."