South Africa's spin attack, particularly in the Test team, will be the most scrutinised aspect of their squad announcement on Thursday as the selectors debate how many and what kind of spinners to take on their upcoming tour to India. South Africa will play three T20s, five ODIs and four Tests across 72 days on the tour.

In Tests, South Africa have rotated through several options without settling on any of them permanently. This gives them sufficient candidates for the India tour but no stand-out performers. Thus, Simon Harmer, Dane Piedt, Imran Tahir and Aaron Phangiso could find themselves in the fray.

Harmer, an offspinner with three Tests to his name, is the closest to an incumbent. He played in South Africa's most recent outing, the rain-affected Tests in Bangladesh, after making his debut against West Indies in January. Harmer, however, would likely not have got that first cap if Dane Piedt, his chief competitor, had not been ruled out through injury.

Piedt had played against Zimbabwe in August 2014, taking eight wickets in an impressive debut. Shortly after that, he suffered what has been described as a career-threatening shoulder injury which required a lengthy recovery. Although Piedt was back in action when Harmer was picked for the West Indies series, it was thought Piedt would need game time to get back to his best and he has since had plenty. Piedt's performances on South Africa A's tour of India - he was their leading wicket-taker with 11 scalps in two four-day games, including a five-for in the first unofficial Test - helped saved some blushes during the heavy losses the team suffered.

Although Piedt has been tipped for a recall, Tahir, who last played the Boxing Day Test against West Indies in 2014, could also make a comeback. That match was Tahir's 16th Test and seemed to be the last, after underwhelming appearances in whites despite his domestic form. But that first-class record - 715 wickets at 26.45 - is exactly why former South Africa left-arm spinner, Paul Harris, thinks Tahir should be part of the Test squad one more time.

"Anybody with those numbers has to be a good bowler," Harris told ESPNcricinfo. "Admittedly, we haven't seen the best of Imran in Test cricket, not even close to it, but he should get one more go on wickets that will suit him."

The selectors will also have to factor in Tahir's fitness. The legspinner withdrew from his commitments at Nottinghamshire after he picked up an upper thigh niggle during the ODIs against New Zealand last month.

The bulk of Tahir's Test career so far has been played in the shadow of South Africa's pace pack, who ran through opposition before Tahir could have the chance. The first time Tahir played in conditions more suited to his style of bowling - against Pakistan in Dubai in 2013 - he took a five-for. His appearances against Sri Lanka recently were disappointing but Tahir still harbours hopes of a Test recall and Harris thinks that in India, Tahir would be an asset.

"On those wickets, you've got to have an out-and-out attacking spinner. The wickets will turn and we've seen how well India's spinners, R Ashwin and Amit Mishra, have been doing. They've been brilliant; South Africa will have to match that," Harris said.

Should South Africa decide their spinner must be used in more of a wicket-taking role, they will have to look elsewhere for a holding bowler but Harris believes the second option will not be too difficult for the team. "They will have Vernon Philander there to keep it tight at one end and then they've also got JP Duminy to do a job," he said.

That will also leave no room for Phangiso, who did not play in Bangladesh despite being a part of the Test squad, or Eddie Leie, the legspinner who made his T20 debut in Bangladesh and has put in good performances for Lions. Harris expects both of them to be part of the limited-overs outfits, where they will likely bowl alongside Tahir.

"Imran has been the go-to man in those formats and that should not change," he said. "But Phangi has also been good in ODIs and T20s, and him and Eddie should both get an opportunity again, especially to decide who goes to the World T20."

With Test cricket and T20 taking precedence, South Africa's one-day cricket has been forced to take a backseat but Harris is concerned with the "up-and-down" form of the ODI side. Since the World Cup, South Africa have lost an away series to Bangladesh and won a three-match series at home against their semi-final conquerors New Zealand despite an unsettled squad. Their No.7 allrounder conundrum remains confusing and David Wiese could find himself overlooked in favour of Chris Morris.

The problem of the opener's spot, which was caused by Quinton de Kock's exclusion, should solve itself. De Kock reeled off three centuries on the A tour of India and Harris believes "all the signs are that he will be back". Should de Kock return, he will take over the gloves and the opening spot in T20s and ODIs, leaving no room for Morne van Wyk in the shorter formats or Dane Vilas in the Test side.

"It will be a pity for Dane because he did not even get the chance to bat in Bangladesh but you've got to go with Quinton in the Tests at No.7. He is so dangerous and so effective," Harris said.

The only other concern South Africa will have is in the Test opening spot, where they recently promoted Stiaan van Zyl. He only batted briefly in that role in Bangladesh but is expected to stay there, with Reeza Hendricks either traveling as a reserve or not at all. AB de Villiers, who missed the Bangladesh Tests due to paternity leave, will be back for all formats while Morne Morkel and JP Duminy, who both recently become fathers, are also available for selection.