Cape Town - Tabraiz Shamsi's 4/33 in the opening ODI against Sri Lanka on Sunday was the latest reminder that he is a major factor for the Proteas as preparations for the 2019 World Cup continue.
The 28-year-old is in the form of his life having finished as comfortably the top wicket-taker in the 2017/18 One Day Cup with 26 scalps at 14.84, while he was also top of the pile in the domestic T20 Challenge with 16 wickets at 15.31.
With returns like that, it was impossible to ignore Shamsi any longer and the decision was taken to give the wrist-spinner a proper run in Sri Lanka.
He has only played in 8 ODIs, but if Shamsi continues to pick up wickets the way he has done over the past 12 months, then his selection in the World Cup squad will become a no-brainer.
Things do, however, have the potential to get complicated.
READ: Why Proteas can only have THREE bowlers
While Shamsi is in the middle of his firmest push in Proteas colours to date, 39-year-old Imran Tahir has been rested for the Sri Lanka tour.
Instead, he has been playing for Durham in the Vitality T20 Blast in England; the venue for next year's World Cup.
The Proteas do not tour England before the 2019 showpiece, making any exposure to English conditions between now and then invaluable.
Over the past four weeks, Tahir has notched up 28 overs in England, taking 11 wickets along the way at an average of 17.00 and an economy rate of just 6.67.
It leaves him as the sixth-highest wicket-taker in the competition, though he has a better economy rate of any of the five bowlers above him.
Tahir's numbers in England may not be earth-shattering, but the fact that he is acclimatising to conditions over there can only be good news for Ottis Gibson and the Proteas brains trust ahead of 2019.
Tahir only has two more matches remaining with Durham, but the experience has allowed him to find some form again after a difficult year in international colours.
It is almost impossible to see the Proteas going into any of their World Cup matches next year with more than a single specialist spin bowler, and right now it looks like that position will go to either Tahir or Shamsi.
Keshav Maharaj is also in the ODI squad in Sri Lanka, but with just 2 matches under his belt in the format, he has a lot of work to do if he is to force his way into the conversation.
Tahir will be 40 by the time the 2019 World Cup comes around, though that is hardly a factor given his current physical condition.
What is perhaps more concerning is the inevitability that, seven years into his ODI career, there is less mystery surrounding Tahir.
In this February's ODI series against India, Tahir picked up just 1 wicket as the visiting batsmen played him with ease.
It was an unfamiliar sight for a man who has, for so long, bamboozled some of the best in the world.
Tahir's contribution to South African cricket cannot be questioned: 85 ODIs and 139 wickets. No South African spinner has more and, for that reason, Tahir must be considered the favourite to crack the nod ahead of Shamsi in 2019.
It is, however, shaping up to be a battle worth watching.
After the Sri Lanka series ends, the Proteas will have another 16 ODIs until the World Cup and that is when the selectors will have to make their decision.
Both Tahir and Shamsi will be given games along the way, and while there is still a long way to go, Shamsi is off to a good start and on the right track.
But if Tahir's proven pedigree begins to shine through once more, it is hard to see the selectors going anywhere else.
It is not something we have been able to say too often over the last 25 years, but the depth in the South African spin bowling stocks is beginning to look very promising.
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