Melinda Farrell and Kartik Krishnaswamy discuss possible changes in India's batting line-up and maybe even a change of guard for the series decider (2:18)

Kanpur, Kolkata, Indore. Rajkot, Visakhapatnam, Mohali, Mumbai, Chennai. Hyderabad. Pune, Bengaluru, Ranchi. And now, Dharamsala. It's fitting that it all ends here, 1317m above sea level, the altitude setting India their final test of endurance in their most grueling home season in decades.

It's almost inevitable that they should be starting this last lap with fitness issues to worry about. The big question revolves around their captain, Virat Kohli, and his troubled right shoulder, but that isn't their only injury worry, or even their only shoulder-related worry.

KL Rahul has been playing the series with pain in his left shoulder, and joked after his Player-of-the-Match performance in Bengaluru that he was happy it restricted his range of movement and kept him from attempting lofted shots too often.

M Vijay missed that Test with a shoulder injury of his own, and on Friday, the eve of the Dharamsala Test, he did not train with his team-mates. He did not participate in their warm-up game of foot-volley, and he did not bat in the nets. When asked about this, the BCCI's media manager said there were no injury concerns around Vijay, and that he was only resting.

Still, it's quite something for three of the top four batsmen in an international top order to be under the same kind of physical issue at the same time.

It's remarkable, heading into the 13th Test of this home season, that India do not have too many other fitness concerns. It's remarkable that their bowlers, in particular, have withstood its demands so well. R Ashwin and Ravindra Jadeja have played all twelve Tests so far, and Umesh Yadav eleven.

Mohammed Shami, who bowled for the second day in a row at the HPCA Stadium nets, seems at the cusp of a full return to action after missing most of the second half of the season with injuries in his right leg. Such is the physical toll of a Test match, however, that India probably will not risk him at such a crucial moment of the series.

Sure, Shami can look sharp in back-to-back 50-overs games for his state side, and frequently look quicker and more threatening than Ishant Sharma in the nets, but can India expect him to bowl 46 overs across two innings, like Umesh did in Ranchi?

In all, Umesh has bowled 330.5 overs this season. That's just under twice his previous maximum for a Test season - 168.3, in 2011-12. This isn't just hard work for India's bowlers - it's unprecedented.

Between them, Ashwin and Jadeja have sent down close to 1400 overs this season AFP

Think, above all, of the spinners. Ravindra Jadeja is utterly inscrutable while he bowls, his eyes hidden behind sunglasses, but there must surely be a tired crease or two around them. He has sent down 684.2 overs this season. His previous best was 263.2, in 2012-13.

Jadeja sits at No. 2 on the all-time list for overs bowled by a bowler in a season. Who's at No. 1? Well, R Ashwin, of course, at 701.3. If he has seemed, at certain points during this series, to lack some of his early-season zip, this is perhaps the biggest reason for it.

Remember, moreover, that Ashwin was advised rest after the Test series against England, since he was suffering from sports hernia. If you're still wondering what that means, ask WebMD. "A sports hernia," it says, "is an injury of the inguinal" - groin - "area caused by repetitive twisting and turning at high speed. This type of hernia occurs mainly in people who play ice hockey, soccer, or tennis."

Repetitive twisting and turning at high speed. That's what top-class fingerspinners put their bodies through in order to give the ball a proper rip. They don't just spin the ball out of their hands, they drive through the crease with their hips, generating torque through their weight transfer and pivot.

If he's still carrying the effects of the sports hernia, it's no wonder Ashwin has looked below his best in this series. He hasn't really got the ball to drift like before, to curve through that deceptive and almost hypnotic arc. And yet, look at his numbers - 17 wickets in three Tests at an average of 28.94. If anyone's complaining, it's because they're judging him by the standards of his own performances from the first half of the season.

Inevitably, India will be judged by those standards too. They came into this series having won eight and drawn one of their first nine Tests of the season. They have lost one, won one, and drawn one since then, and how they finish could change the meaning of everything that went before.

India have sore shoulders, knees and groins, and a whole lot of tired minds. They have one more Test to play, and one last lap to run.