The 17-year-old outpunched his more fancied rival 5-0 to record a rare Indian triumph over a Cuban boxer.
"Two of my fellow Indian boxers had lost to Cubans earlier in the tournament, I wanted to extract revenge and I am glad I could do it. It is very satisfying to beat stronger and better rivals, especially if it happens to be a Cuban," Sachin told PTI from St Petersburg after the brilliant triumph.
The lanky teen, who once again put his powerful left jab to good use, displayed brilliant ringcraft against his shorter and often clueless opponent.
India thus finished the tournament with one gold and a bronze, a marked improvement from the solitary bronze won in the 2014 edition. Naman Tanwar (91kg) had settled for a bronze after losing in the semifinal yesterday.
More From This Section
"Our young boxers Sachin and Naman have made India proud by winning medals in the Youth World Championships. I hope these cash awards will encourage them to do even better in future. This is the first step towards our country reclaiming its rightful place as a boxing power in the world," BFI President Ajay Singh said.
The class 12th student, who had been in peerless form through the tournament, was not the least bit intimidated by the higher-rated Cuban.
With his height and reach giving Sachin a distinct advantage, the Indian controlled the bout with flawless footwork.
In fact, his strategy of swaying back and forcing Grinan to lunge forward worked brilliantly as the Cuban found it difficult to keep his balance.
Grinan tumbled twice, quite awkwardly, during the bout.
"Sachin used his height advantage quite well. He was in tremendous form through the tournament. It was truly an exceptionally good performance," said coach Lalit Prased, who is with the team in Russia.