Saha over Pant would make sense, if Saha had one bout of injury and then recovered within a few months and came back. I believe there is an unsaid policy that if your frontline player is coming back from injury, then he will be given a chance in the playing XI. I have read this in some articles quoting our selectors.
But then Saha went on and got injured again, twice. And now has been out of the team for almost 2 years. Meanwhile, Pant has racked up a couple of tons in Australia and England, and despite questions on his temperament, he has actually shown that he can survive tough bowling line ups - all he needs is some guidance at the other end to churn out big scores. All this is undoubtedly unfortunate for Saha, who was our first choice keeper since Dhoni retired. But this just goes on to show, how important fitness level is if you are part of a world class team. An injury episode and you might mess up your career completely.
For now, Pant has to be persisted with in Tests and Saha will have to play the backup role. Pant's fitness is excellent as well, which can make up for his average keeping techniques. He is stocky but very agile. Should definitely be in the starting XI tomorrow