Last week against Central Catholic, Upper St. Clair caused four turnovers in a 38-0 win.
Friday night against Woodland Hills, it was the Panthers who had trouble keeping possession.
Upper St. Clair turned the ball over six times, three of which led to first-quarter touchdowns for the Wolverines, and Woodland Hills avenged a season-opening loss with a 42-20 win in a WPIAL Class AAAA semifinal at Baldwin.
Woodland Hills (10-2) will play North Allegheny in the WPIAL title game Friday at Heinz Field.
"We got some turnovers early and we were able to capitalize on them and get some early scores," Woodland Hills coach George Novak said. "[Upper St. Clair] is a very good football team. We're very fortunate."
The mistakes started for the Panthers from the opening kickoff.
Upper St. Clair's Steve Mackowick fumbled the kick, and Woodland Hills recovered at the Upper St. Clair 14. It led to a DeQuan White 1-yard touchdown run.
Another special teams gaffe by the Panthers led to the Wolverines' next score.
Upper St. Clair (11-2) was forced to punt after gaining 3 yards on three plays on its first possession, but the snap couldn't be handled by punter Tim Witenske and the ball rolled to the Upper St. Clair 5. Witenske picked up the ball but was tackled on the spot by a host of Woodland Hills defenders.
Two plays later, Alex Beasley found the end zone on a 3-yard run.
"You can't give a good team like that the ball deep in your own territory twice," Upper St. Clair coach Jim Render said. "It wasn't our night. We were outcoached and outquicked."
Mackowick lost another fumble later in the first quarter, which led to a 25-yard touchdown by sophomore Art Thompkins. Thompkins entered the game having carried the ball three times all season but got more work Friday because starting running back Miles Sanders missed the game with a neck injury he sustained last week against Gateway. Sanders had 36 rushes for 204 yards and three touchdowns in the first two playoff games.
Down by 21, Upper St. Clair quarterback Pete Coughlin rallied the Panthers before the half, tossing touchdown passes of 59 yards to Morgan Lee and 20 yards to Mackowick to cut the deficit to 7 at the half.
It looked reminiscent of the Panthers' 31-12 win Aug. 31 against Woodland Hills, when the Wolverines led, 12-0, in the first half, but Upper St. Clair scored the final 31 points for the win.
"Our kids came out in the second half and made sure that didn't happen again," Novak said.
The Wolverines increased their lead by going to the air in the final 24 minutes.
After throwing one pass in the first half, Wolverines quarterback Cody McClelland completed 4 of 5 passes for 63 yards on the opening drive of the third quarter, including a 31-yard touchdown pass to Khalil Harper to make it 28-14 after the extra point.
After Coughlin threw his fourth interception of the game, McClelland threw his second touchdown pass, an 8-yard toss to Tom Greene.
McClelland finished 8 of 13 for 156 yards, and Greene had a game-high five receptions for 120 yards and also had an interception.
Trevon Mathis added two interceptions, one of which he returned 50 yards for a touchdown.