4 reasons the Sri Lanka Test series is preparation for the South Africa tour

India's KL Rahul dismissed by Suranga Lakmal (L)

India are currently en route to Nagpur for their second Test of the three-match Test series against Sri Lanka, and will face off against the Lions at the city's Vidarbha Cricket Association Stadium.

Following Sri Lanka's tour of India, the team will Tour South Africa through January and February of 2017, leaving them with a very short gap before they resume play.

But several factors indicate that Sri Lanka's tour of India will be good preparation for their early 2018 tour of SA.

Here's why:

The search for the seamers begins

Mumbai and former India seamer Shardul Thakur could be the need of the hour

A grassy wicket is always helpful for seamers - and there is little doubt that captain Virat Kohli will want to play some quality pace against the big-hitting South African batsmen. In view of this, Kohli - and selectors - will await the return of Bhuvneshwar Kumar, who is currently on hiatus for his impending wedding.

Although Bhuvneshwar sits out the remainder of the SL series, he will likely be expected to return for South Africa; he led the attack in the first Test against Sri Lanka, and earned Player of the Match for his 8 wickets and economical bowling, particularly in the second innings.

But given the bouncy, grassy pitches Shastri and Co are expecting in South Africa, India will specifically want a seam attacker rather than just pace, although pacers have been successful on the surface.

With no specific seamer currently on the squad, India could possibly look to Shardul Thakur who fits that bill well. The left-arm seamer has done well at Ranji and made his ODI debut against Sri Lanka this year, but does not have much Test experience. Thakur was named to India's Test squad for their tour of West Indies last year but remained on the bench, and so perhaps lacks international exposure.

But that does not necessarily mean he is out of form. The 26-year-old, who so far has had his biggest successes in first class cricket, led his team - Mumbai - to the Ranji Trophy title in the 2015-16 season with an eight-wicket haul against Saurashtra.

Thakur has also been active in the IPL, and although the format may not necessarily prepare him for the Tour, it has ensured he has not been absent from the game in terms of play or fitness.

Hyderabad bowler Mohammad Siraj also recently made his debut for India against New Zealand during the teams' T20 tournament in India, and like Thakur did well at Ranji cricket as well as the IPL. Siraj, although not a dedicated seamer, can bowl seam and did take a wicket on international debut. Younger than Thakur, Siraj is also relatively less experienced in that regard, but grooming both these players for seam will no doubt bolster India's bowling attack.

A proper test of fitness

Ravi Shastri brought back the yo-yo fitness test as Team India's coach

Following the appointment of Ravi Shastri as the coach of Team India, fitness rules were tightened significantly, with the old 'Yo-yo fitness test' being reintroduced. A number of players saw an ouster from the side as a result, among them Yuvraj Singh.

Now, with their plates full in terms of tournaments and only a short break between what has been a packed few months, those who passed the yo-yo fitness test and made the cut, will have that fitness tested to its limits. While Tours in their home country may be marginally easier, the stress of playing multiple 5-day tournaments will take its toll.

That, coupled with travel and the dry heat in South Africa will exact Indian players once the series rolls around - and will separate the men from the boys on the Tour.

With several players - older and younger, not firing as well as they need to be on the pitch, this may be one of the biggest factors involved.

Spinners will be put to the test

Ravichandran Ashwin has not had the best form of late

India's spinners have traditionally done well on drier, flatter tracks - which makes it surprising that BCCI team management wanted the SL series to be a test for them, considering they asked specifically for grassier pitches. But the spinners have done well once the Test progresses and the pitch dries up, which should be similar to conditions in South Africa.

Ravichandran Ashwin is among those struggling for form at the moment, as is Ravindra Jadeja - and the Indian spin duo went without a wicket in the first Test.

Ashwin was economical in his bowling spell in the first innings, but only spent 8 overs with the leather, while Jadeja bowled an over in each innings as the pacers took centrestage.

The two were dropped from the ODI side owing to lacklustre performances in the seasons leading up to India's series against New Zealand and after that, Sri Lanka for the ODI series. The two initially started as ODI specialists and since moved to focus on Tests, but now are failing to fire here.

South Africa could be the make-or-break for spinners in general, and Ashwin in Jadeja in particular.

Test for openers to bat on tricky pitches

Shikhar Dhawan has recused himself from the second Test against SL

India's Test openers have been hit-and-miss this season, and even within the same match. Both KL Rahul and Shikhar Dhawan got out cheaply - Rahul for a duck - in the first innings, but managed to come back in the second as they formed two of only three players who took India to a significant total.

Rahul in particular had been having quite the purple patch of form ahead of his opening stint against Sri Lanka, but has in his own words "failed to build to 50s and 100s frequently."

Dhawan did not do as well coming into the Test, and in fact came in on the back of an extended hiatus to support his wife through health issues. The usually explosive opener, who has proved his mettle across formats, has recused himself along with Bhuvneshwar Kumar for the second Test.

(Bhuvi will also sit out the remainder of the series as he is due to get married soon.)

If Dhawan makes the cut to open on Tour in January (which it seems likely he will do), he will have a task ahead of him on the grassy pitches, given their propensity for providing for low-scoring games.

It is possible Abhinav Mukund, who has relatively less experience on the international Test stage, could partner Dhawan in the opening slot, and that will pose a strong test to the openers - especially should South Africa ask India to set a total first.