Manoj Kumar of India has battled past Turkmenistan's Serdar Hudayberdiyev in the opening light welterweight contest of the evening.
Kumar made the brighter start, but was caught with a straight right hand as Hudayberdiyev settled into the contest, tying the score at 2-2.
Once again, the Indian made a faster start but faded as the round wore on, with the Turkmenistani rattled in a venomous three-punch combination.
However, Kumar regained the upper hand with a straight right that scored well, before exploding off the mark with another massive right that forced Hdayberdiyev to back off.
Kumar held a four-point advantage in the last, so Hudayberdiyev went on the attack, desperate to keep his Olympics alive.
The Indian sealed his passage into the last 16, where he will meet Great Britai';s Tom Stalker, with a 13-7 decision.