Humbled in Indore, an outright victory in Ahmedabad will seal India's place in the World Test Championship final against Australia but if Rohit Sharma's team loses or plays a draw, its fate will depend on the outcome of the Sri Lanka-New Zealand series.
Australia by virtue of their nine-wicket win in Indore have already qualified for the grand finale at the Oval from June 7-11.
Australia are sitting atop the WTC table with 68.52 percentage points (PCT).
Also Read — We talk too much about pitches in India, why change when we are getting the results: Rohit Sharma
Percentage points are calculated when points earned by a team are divided by the points contested for.
A team earns 12 points for a win, four for a draw and six in case it's a tie.
As of today, Australia have 148 points by virtue of 11 wins and four draws from 18 matches. Playing for 216 points on offer, they have a PCT of 68.52.
Even if Australia lose the fourth and final Test against India, they would still remain on top with 64.91 PCT (148/228×100).
What happens to India
India's PCT is 60.29 after earning 123 points in 17 Tests (10 wins and 2 draws) so far. India have lost a few points during the course of this cycle due to slow over rate.
If India win the last Test, their PCT will go up to 62.5 with 135 points from a maximum of 216 on offer (18 Tests). They will then retain their second position and will qualify for final.
However, in case of a defeat, India's PCT will drop to 56.94 and then they will have to depend on the result of Sri Lanka's away-series against New Zealand. In case of a draw, India's PCT will drop to 58.79 and even then they will have to wait for the result of the Sri Lanka-New Zealand series. Ditto in case of a tie where India's PCT will be 59.72.
How can Sri Lanka qualify
Sri Lanka's only shot at the final qualification will depend on a 2-0 victory in New Zealand which is one of the toughest away assignment for sub continental teams.
Sri Lanka's current PCT is 53.33 with 64 points from possible 120 (10 Tests).
If India happen to lose, draw or tie final Test and Sri Lanka win the series 2-0, their PCT will be 61.11 with 88 points from a maximum 144 points at stake. But if Sri Lanka draws even one game and win 1-0, their maximum PCT will be 55.55 which will be less than what India (56.94) will have even if they lose the final Test.