Purdy (9-5) entered the game reeling from a last second loss earlier in the week against Seneca.
Pierce City (6-7) was looking for a victory over a district foe.
Stunned momentarily, Purdy responded in a big way.
Alex Mareth, Austin Hancock and Cameron Terry kicked off an 8-0 push that ballooned into a 22-4 run, ending at the 5:15 mark of the second period with Purdy ahead 23-13.
"I think we relaxed just a bit when we took the early lead," said Pierce City coach Matt Street. "Purdy has several scorers, and they showed they could score in a hurry."
Purdy claimed a 22-13 lead after one period and carried a 38-24 margin into halftime.
Purdy used its depth to build the first half-lead. The bench play of Hancock and Mareth outscored Pierce City 20-0 and proved to be the difference in the game.
"Austin and Alex brought a lot of energy and excitement to the floor," said Purdy coach Tommy Egan. "We don't consider them bench players. They really are starters that have to wait to play. It is nice to have that kind of depth."
The third period was a seesaw battle that hovered around a Purdy 10-point lead.
Six times in the third quarter Pierce City cut the advantage to 9 points only to see Purdy re-establish a double-digit lead.
Purdy opened the fourth quarter leading 48-38. A layup by Pierce City's Cody Fitchpatrick helped the green and white initiate a 17-7 run to trail 59-55 with 1:52 left in the game.
A 3-point play by Terry pushed the Purdy lead back to 7 points, helping the black and gold secure the victory.
"I'm proud of the way we responded when Pierce City pushed back in the fourth quarter," said Egan. "We had several guys step up and make plays all night long. That is what it takes to win games."
Scoring for Pierce City: Hyde, 24 points; Fitchpatrick and Kole Kelley, 13 each; and Cedric O'Hara and Colton Drollinger, 3 apiece.
Scoring for Purdy: Terry, 17 points; Brent Cornman, 15, Mareth, 12; Keevin Walker, 11; Hancock; 8 and Glenn Scott, 4.