Nate Desens made mincemeat of the two easiest holes on the inward nine at Mill Creek on Tuesday afternoon.
The Geneva senior drove the green of the short par-4 10th hole to record a simple birdie.
But Desens' signature moment in his career-low 2-under par 34 came on No. 17, where he hit his 5-iron approach from slightly under 200 yards to within three feet of the pin.
The resulting eagle enabled Desens to turn back Batavia senior Jacob Piechota by 2 shots for medalist honors in the Vikings' 149-155 victory in Geneva.
With their fifth consecutive Upstate Eight Conference River Division victory, Geneva also extended its season-long dual-match winning streak to eight.
"I thought (my second shot on No. 17) was going to be on the green, but I didn't think it would that close," said Desens, who dropped his lone shot on the devilishly tough 16th hole.
Geneva (8-0, 5-0) tamed its archrival with depth and consistency.
Freshman sensation Graham Lillibridge fired a 39, and his score was discarded.
Second-ranked senior Brett Hassels, fifth-man Danny Cisco and sixth-player Matt Fisher all recorded 2-over 38s to keep the Vikings' record unblemished.
"This is a great home-course advantage for us," said Geneva assistant coach Bryan Knapp, who was filling in for Bill Koehn. "Over the course of the last decade, 12 years I don't think we have lost more than one or two matches here."
Course knowledge is the central ingredient to the Vikings' home cooking.
"We're familiar with the course," Hassels said. "It's kind of a funky course. You have to know where to hit it."
St. Charles East is the last team in the Vikings' path for a perfect run in the River Division.
Piechota was ruing two very relatively short misses, including one for birdie in his final hole of the modified shotgun start, but the senior still fired his fourth straight level-par round.
"They're a very tough team to beat, especially at (Mill Creek)," Piechota said of Geneva. "Anyone in their lineup from (Nos.) 1 through 8 can go low at any time. I didn't putt bad today. I just didn't putt the way I wanted to. I was misreading the greens."
Batavia (3-3, 2-2) received matching 39s from Nick Bleidorn and Nick Robinson.
Andrew Nelson -- one of three sophomore starters for the Bulldogs -- turned in the fourth counting score for Batavia with a 41.
"I thought 150 would be the number," Batavia coach Tim DeBruycker said. "It wasn't the case today. (Desens) played a great round for them today. Thirty-four is a very good score, even it is on your home course."