Kumar rallied from 1-3 to fashion a memorable win over his seasoned rival in a Group B match at the Khar Gymkhana.
In other league ties, world billiards champion Pankaj Advani and world No 21 Stephen Lee of England cruised to their second wins in as many outings.
Playing only his second league match, Merchant ignored the loss of the opening frame and raced to a comfortable lead, clinching the third frame on the black and then pocketing the next with a lucky black pot and surge to a commanding 3-1 lead.
Lee fired consistent breaks against Aayush Kumar of Punjab for his second win in Group A, while Advani and Aditya Mehta lived up to their reputations and warmed up for sterner tests ahead.
