Defending champion Sargon Isaac has been sensationally knocked out of this year's United States National Snooker Championship in the round of 16 by former champion Ajeya Prabhakar, who now goes forward to book his quarterfinal berth at the New York Athletic Club (NYAC) in Manhattan, New York.

With Prabhakar demoralized with his form following his third place position in Group C, he was feeling very low on confidence but he has a record of playing well against his fellow Californian, which included a remarkable 4-0 defeat of Isaac in the semifinals of the 2012 Championship of which he went on to win.

It was a solid performance by Prabhakar who was a totally different player than he was in his groups as he decisively won each of his frames with respective breaks of 37, 46 and 38 to chalk up a wonderful 3-1 success.

Number two seed Ahmed Aly Elsayed, who squeezed into the round of 16 after finishing third in Group B, faced a very capable opponent Wenpei Zhu who won Group C, but he safely came through 3-1 for his appearance in the quarterfinals.

Brooklyn's Raymond Fung, twice a runner-up in this Championship, has gone about his business in a cool and calm manner with little fuss, with the number four seeded player carrying on his excellent form with a great 3-1 victory over Mark White from Texas, who himself came into this Championship as a possible title contender but has failed to perform much to his disappointment.

Renat Denkha was very impressive throughout Group B defeating Aly along the way to win the group, and while he has a close first frame against Louis Pannullo he wrapped up the match for a 3-0 victory.

The improving Laszlo Kovacs, who won Group E to secure his place in the round of 16, defeated debutant player Li Hua Chen, who was runner up in Group C, 3-1 to book his second successive quarterfinal appearance. California's Mihai Visovan, who came through as Group F winner, fell to Saif Ibrahim 3-0, the debutant player from Michigan who was runner-up in Group D.

Omar Balsara is a former United States Snooker Association (USSA) Tour winner competing in his first National Championship, and he has certainly shown his skills by defeating Aly in the group phase and going on to advance into the quarterfinals with a 3-0 win over the very experienced Terry Dunne.

Laszlo Kovacs, a quarterfinalist in last year's Championship from Astoria, New York, went through the group undefeated for the loss of just one frame, just ahead of New Jersey's Rizwan Khan. NYAC member Louis Pannullo edged through in third place, and then went on to win a playoff match 2-0 against the Group F third placed player, Zachary Ridgway, to advance into the round of 16.

Ian O'Mahony will make his second appearance in the Championship quarterfinals in three years, after the NYAC member, who came through as Group A runner-up, went through with a tense and edgy 3-2 win over New Jersey's Rizwan Khan.

The round of 16 results as follows:

Round of 16 (Best-of-5 frames)
Match ID	Player		Player
R16-1	Sargon Isaac (California) 1	1 - 3	Ajeya Prabhakar (California) 3
R16-2	Omar Balsara (Virginia)	3 - 0	Terry Dunne (New York)
R16-3	Raymond Fung (New York) 4	3 - 1	Mark White (Texas)
R16-4	Laszlo Kovacs (New York)	3 - 1	Li Hua Chen (New York)
R16-5	Renat Denka (Illinois)	3 - 0	Louis Pannullo (New York)
R16-6	Ian O'Mahony (New York)	3 - 2	Rizwan Khan (New Jersey)
R16-7	Wenpei Zhu (New York)	1 - 3	Ahmed Aly Elsayed (New York) 2
R16-8	Mihai Visovan (California)	0 - 3	Saif Ibrahim (Michigan)

The quarterfinals draw as follows:

Quarterfinals (Best-of-7 frames)
Match ID	Player		Player
QF1	Ajeya Prabhakar (California) 3	vs.	Omar Balsara (Virgina)
QF3	Raymond Fung (New York) 4	vs.	Laszlo Kovacs (New York)
QF3	Renat Denkha (Illinois)	vs.	Ian O'Mahony (New York)
QF4	Ahmed Aly Elsayed (New York) 2	vs.	Saif Ibrahim (Michigan)

The winner of the Championship will be crowned the 2017 United States National Snooker Champion, and alongside the runner-up will gain automatic selection to represent the United States at this year's International Billiards & Snooker Federation (IBSF) World Snooker Championships which will take place in fall in Malta.

Full coverage of the 2017 United States National Snooker Championship will continue here on SnookerUSA.com.