It was the Indians' first win over Rustin, the four-time defending American Conference champion, since 2007.
"It feels great to finally get Rustin off our back," said Tom Pancoast, a senior quarterback and free safety. "We got it done when we had to."
Pancoast, the focal point of a multiple-I offense, carried 20 times for a season-high 204 yards and two touchdowns.
Said Clark, who team last captured the American Conference crown in 2007: "He's a really good athlete. He's a kid that wants the ball."
In the first quarter, the 6-foot-4, 195-pound Pancoast broke free for an 85-yard TD. "It was a read up the inside, and we had some nice blocking on the outside by [wide receivers] Patch Johnson and Sean Barnes," he said. "I think I was untouched."
Early in the second, the Golden Knights put together a nine-play, 77-yard drive to forge a 7-7 tie. Dave Fithian's 47-yard pass to wideout Dan Walls set up Adam Burke's 4-yard burst off right tackle.
Unionville (3-1) opened the second half with a 12-play, 80-yard scoring march. On fourth and goal from the 1, Pancoast lowered his shoulder and found pay dirt.
"Once we got down around the goal line, we had to fight for every yard," Pancoast said. "It felt good to finally punch it in."
On the conversion attempt, holder Alex Pechin mishandled the snap and was dragged down by Brendan Dougherty, leaving the door open for Rustin (3-1) to eke out a one-point win.
Late in the fourth quarter, the Golden Knights, who were held to 106 rushing yards, advanced to the Unionville 25 on a hook-and-ladder play. But an unsportsmanlike penalty that followed it moved the ball back to the 40.
On fourth and 12 from the 40, Fithian's pass across the middle was deflected by linebacker Zach Barnes.
West Chester Rustin 0 7 0 0 – 7
Unionville 7 0 6 0 – 13
U: Tom Pancoast 85 run (Sean Barnes kick)
WCR: Adam Burke 4 run (Dylan Jenkins kick)
U: Pancoast 1 run (run failed)
Contact Rick O'Brien at email@example.com, or @ozoneinq on Twitter.