Saunders stayed patient against Starbala's spoiling tactics
Billy Joe Saunders moved to within two wins of an Olympic place after a tense 13-12 victory over Michal Starbala.
He struggled to get to grips with the awkward Pole whose infringements went unpunished until a crucial final round.
Two two-point penalties eventually turned the fight in Saunders' favour in the Olympic qualifying event in Italy.
GB coach Terry Edwards said: "I counted over 15 cautions from the referee to the Pole before he took points away, but Billy Joe's attitude was superb."
Welterweight Saunders, 18, trailed 8-4 at the end of the third round but the Briton finally exhausted Starbala who was forced into holding him.
I got the job done and I feel like I'm making the weight better
than I've ever done
He said: "The Pole was tougher than I thought. He had been told to hit and grab, but I stuck to my game plan and came through."
Saunders, bidding to become the fifth GB boxer to book a Beijing berth, will next face another awkward opponent in Georgia's Kakhaber Zhvania.
Bantamweight John Joe Nevin, 18, outpointed Croatia's Ahmeti Mirsad 23-8 to move closer to securing Ireland's second Olympic berth.
Former European bronze medallist Stephen Smith also moved into the last eight after surviving a scare in the featherweight division against Ireland's
John David Joyce.
Smith breezed into a 19-7 lead at the halfway point but Joyce's grand finale
almost paid off.
Smith said: "I got the job done and I feel like I'm making the weight better
than I've ever done."
James DeGale eased though his second middleweight contest by outclassing
Spain's Abella Castillo midway through round three.
He next faces Ireland's Darren Sutherland, who came from behind to beat Azeri Rahib Baylarov.
Mo Nasir will meet London's Khalid Yafai in an all-British flyweight
quarter-final after the young Welshman skipped his way to a clear 19-9 victory
over Romanian Julius Pozco.