Leach did not take part in the tourists' net practice on Wednesday, joining his team-mates at the ground solely to receive treatment on his left knee injury.
The Somerset spinner picked up the problem when he jarred his leg while fielding on the first day of England's remarkable victory in the series opener and later aggravated it as he tried to play through the pain.
Despite suffering from bad bruising and swelling around the joint, he continued to play a reduced role in Hyderabad, contributing the wicket of Shreyas Iyer as the tourists pressed for the win.
But he was visibly limping as he watched the squad go through their paces ahead of Friday's clash and would need to rally quickly to have any chance of being considered.
Captain Ben Stokes hailed Leach as a "warrior" for battling through last week and opener batter Zak Crawley is not ruling out an unexpected recovery.
"He's a tough kid, Leachy, so I'm not sure. You never know with Jack," he said.
"You can never really write him off. We'll see how he pulls up in a couple of days."
While his injury looks set to scotch head coach Brendon McCullum's mischievous suggestion that England could all of their spinners in a seam-free attack, it does raise the chances of a debut for his Taunton team-mate Shoaib Bashir.
The 20-year-old, who has just six first-class caps and 10 career wickets to his name, was a belated arrival in India after visa complications related to his Pakistani heritage forced him to return home to London.
But, after banking some unwanted air miles, he is back with the squad and played a full part in training. Rehan Ahmed, the leg-spinning all-rounder, sat out the optional session but is understood to be fully fit.
Despite Bashir's gossamer-thin track record, he impressed during the pre-series training camp in Abu Dhabi. Tom Hartley's nine wickets on debut in Hyderabad, meanwhile, are unlikely to deter England from backing another hunch.
"He's a great kid. He's got a lot about him," Crawley said.
"He knows what he is trying to do with his bowling and he backs himself. I like that and feel like if he got his chance in this series he would go well."
India have had injury problems of their own, losing the world's number one all-rounder Ravindra Jadeja and KL Rahul after the first Test.
Their most glaring absentee remains Virat Kohli, who top-scored with 167 when England played their only previous Test in Visakhapatnam seven years ago, and remains unavailable due to personal reasons.
There is a growing feeling that the wind is blowing in England's direction but Crawley, who was part of the side who went from 1-0 up to a 3-1 defeat here in 2021, is keen to not get carried away.
"Whoever they pick, they're going to be a very good team," he said. "They're a top side in their own conditions.
"There's four games left and we need to stick to what we do well. Hopefully the results come from there but we're not getting too far ahead of ourselves.
"We're preparing for this one like it's the first game, we're staying where our feet are and we'll see where that takes us."
