Much of the attention going into Saturday’s WPIAL Class 3A semifinal between No. 1 Shady Side Academy and No. 4 Avonworth centered around the Bulldogs’ acclaimed freshman duo of Karis Thomas and Maggie Spell.

By the time the final horn sounded, though, it was Greta O’Brien who stole the show.

The Antelopes’ 5-8 sophomore guard scored 15 of her game-high 17 points in the second half — right above her average of 15.6 ppg for the season — displaying a smooth shooting touch along with a natural ability to get to the hoop and a willingness to fight through contact to get there. Her gutsy performance helped Avonworth (18-5) become the first team on either the boys or girls side to eliminate a No. 1 seed this postseason with a 41-35 win against Shady Side (22-3) at Montour High School.

“All of them are good. They all are great shooters and they all can dribble,” O’Brien said about the Shady Side stars after the game. “We just really had to keep an eye on [Spell] and [Thomas] with her ball-handling. They all made really great plays, so it was definitely tough to defend them, but we kept them under control.”

After the Bulldogs took a 16-15 lead into the half, the Antelopes began to seize control of the momentum in the third quarter. A buzzer-beating corner 3 by O’Brien gave them a 29-25 advantage heading into the fourth, and she was just getting started.

With Avonworth leading, 31-25, senior Cate Sauer and sophomore Cameron Capel hit a pair of big shots for Shady Side to make it a one-point game early in the fourth. But O’Brien answered with a 4-point play by making a basket while drawing a foul, then corralling her own rebound and scoring after missing a free throw to make it a 37-32 Antelopes lead.

Thomas hit a deep 3-pointer to make it 37-35 with 3:49 to play, but the Bulldogs would not score again as Avonworth’s vaunted defense closed out the 41-35 win with several key stops.

“Personally, I like the underdog role,” Antelopes coach Nick Dizon said. “Our girls were confident they could win. They knew we had to play well, but they were confident we could win, and we kind of embraced it a little bit.”

In his first year as coach at Avonworth after coaching the previous four years at Kiski Area, Dizon now has the Antelopes one win away from claiming their seventh WPIAL title, although it would be their first championship since 2005. They will face No. 2 Laurel in the Class 3A championship game at 3 p.m. Friday at Petersen Events Center.

“I couldn’t be more proud of them,” Dizon said. “Our first game seems like it was forever ago. How much we went through to get us to this moment — obviously, we’re happy to be going to the Pete, but the journey to get here has been fun.”

Other Class 3A girls semifinal

• No. 2 Laurel (23-2) emerged victorious from its rubber match vs. two-time defending WPIAL champion Neshannock (18-7) in convincing fashion, ending the No. 3 Lancers’ reign with a 66-46 win at Ellwood City High School. Star senior Mairan Haggerty finished with 26 points for Neshannock to lead all scorers, but it wasn’t enough to overcome the Spartans’ balanced attack led by 23 points from Johnna Hill, 15 from Reagan Atkins and 14 from Joselyn Fortuna.

Class 2A girls semifinals

• Playing without four-sport standout Shaye Bailey, who is out with a collarbone injury, No. 2 Freedom (20-4) earned a return trip to the WPIAL championship game by gutting out a 47-44 win against No. 11 Aliquippa (12-10) at Beaver Falls High School. Star senior Julz Mohrbacher did the heavy lifting for the Bulldogs with 33 points and 11 rebounds, while Aunesty Johnson led the Quips with 23 points in the matchup of Section 1 foes.

• It will be an all-Section 1 showdown in the final, as top-seeded Shenango (21-4) advanced to force a rubber match against Freedom at 7 p.m. Thursday at Petersen Events Center. The Wildcats trailed by two entering the final quarter before outscoring No. 5 Burgettstown (19-6) in the fourth, 18-6, en route to a 54-44 win at Beaver Falls.

Class 5A boys semifinals

• Top-seeded Peters Township (22-3) extended its winning streak to 15 games in a row with a 62-55 triumph against No. 4 Gateway (17-6) at Mt. Lebanon High School, earning a trip to Petersen Events Center for the Class 5A championship game against No. 2 Penn Hills at 9 p.m. Thursday. Jack Dunbar scored a team-leading 29 points to go with 15 from Jake Ziegler and 11 from Brendan McCullough in the Indians’ win.

Class 1A boys semifinals

• Alier Maluk scored 21 points and pulled in 12 rebounds to lead four double-digit scorers for No. 1 Imani Christian (17-6) in a 75-57 win against No. 4 Geibel Catholic (17-7) at Mt. Lebanon. Dame Givner and Avery Wesley added 14 points apiece while R.J. Sledge finished with 13 for the Saints, setting up a much-anticipated clash of the top two seeds in Class 1A at 5 p.m. Thursday at Petersen Events Center.

• Sophomore Lucas Stanley scored a team-leading 26 points and older brother Matt Stanley finished with 22, offsetting a game-high 27 points from Chase Jones of No. 3 Carlynton (16-7) in an 80-58 win for No. 2 Union (22-2) at Montour High School. The win sends the Scotties back to the WPIAL championship game for the second year in a row, where they will attempt to win their first WPIAL title since 2003.

Boys scores

Class 5A semifinals

Penn Hills 67, North Hills 51

Peters Township 62, Gateway 55

Class 1A semifinals

Imani Christian 75, Geibel Catholic 57

Union 80, Carlynton 58

Class 4A consolation first round

Hampton 56, South Allegheny 50

Uniontown 70, Belle Vernon 58

Class 3A consolation first round

Seton LaSalle 77, Mohawk 68

Shady Side Academy 53, Yough 51

Girls scores

Class 3A semifinals

Avonworth 41, Shady Side Academy 35

Laurel 66, Neshannock 46

Class 2A semifinals

Freedom 47, Aliquippa 44

Shenango 54, Burgettstown 44

Class 1A consolation first round

Avella 53, Eden Christian 51

Monessen 56, West Greene 53

For WPIAL postseason basketball brackets, results and schedules, go here:

Steve is a sports writer at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at srotstein@unionprogress.com.

Steve Rotstein

Steve is a sports writer at the Pittsburgh Post-Gazette, but he's currently on strike. Email him at srotstein@unionprogress.com.