Shardul Thakur has been an average bowler for team India in T20s and some ODIs. However, he is not a dependable bowler like Bumrah and Shami which is why he has to sit out of a lot of matches and get selected as a replacement. At times he has shown his worth with the ball to Indian Management by taking wickets of some skilled batsmen by bowling superbly well. He was once included in the Test team in 2018 but did not take any wickets there.
T. Natarajan is the new sensation who has impressed many cricket fans and also the selectors in the BCCI. He made his T20 debut for the last two T20 matches against Australia and showed everyone that they have another young and promising bowler who can bowl at par with someone as good as Bumrah. Natarajan took 6 wickets in the 3 T20s that he played against Australia.
Navdeep Saini is the one who is most favourable to replace Umesh Yadav. He has raw pace and can also swing the new ball in the initials overs. His pace also gives him the advantage to reverse swing the old ball. Saini has performed well in the IPL as well as the T20s playing for India. He is the best fit to replace someone like Umesh Yadav in the team.