Rahul was hit on his hand by a throwdown by Rathour ahead of the second Test.
Rohit Sharma, the regular skipper was already ruled out of the second Test after he had hurt his thumb during the second ODI in Dhaka and missed the first Test, while he didn’t recover in time for the second match.
India is already without two key fast bowlers in Mohammad Shami and Jasprit Bumrah on this tour, with Bumrah recovering from his back stress reaction and Shami injuring his shoulder just before the Bangladesh tour began. Also Navdeep Saini was also ruled out due to abdominal strain.
All-rounder Ravindra Jadeja was named in the squad but had to miss the tour after failing to recover in time from his knee injury which led to him missing the T20 World Cup 2022 as well.
While India batting coach Vikram Rathour indicated on Wednesday that Rahul's injury wasn't serious, he did not confirm whether he is certain to start the match.
"It doesn't [look serious]. He seems to be fine. Hopefully, he'll be okay. The doctors are looking at it, but hopefully, he'll be okay,” Rathour said in his pre-match press conference.
Rathour, incidentally, was delivering throwdowns to Rahul when he took the blow to his hand towards the end of his nets session. He was seen rubbing the injured area and was attended to by the team doctor.
In the worst-case scenario, if Rahul doesn’t recover in time for the second Test, vice-captain Cheteshwar Pujara will lead the side in his absence, and in place of Rahul as an opener, Bengal’s Abhimanyu Easwaran could make his India Test debut.
Easwaran was added to the Indian Test squad as a replacement for Rohit Sharma after he had an amazing A tour of Bangladesh. Abhimanyu made back-to-back hundreds in the four-day games against Bangladesh A in Cox's Bazar and Sylhet.
India lost that ODI series 2-1, and lead the two-Test series 1-0 after a 188-run win in Chattogram.
(ESPNCricinfo inputs)