The eighth-seeded Bucksport Golden Bucks concluded a weekend of major high school playoff upsets by posting a 1-0 victory over No. 1 Maine Central Institute in an Eastern Maine Class B schoolgirl soccer quarterfinal in Pittsfield Monday.

Trisha Beaulieu of Bucksport was credited with the game’s only goal 1:15 into the second half when her kick was touched by an MCI defender and deflected past goalie Jesse Brookes.

Brookes had come out to play the ball and was unable to reverse direction when the ball’s path was changed.

“To tell the truth, I couldn’t tell if it was a pass or a shot,” said Bucksport coach Mark Johnson. “It was on the far side and I couldn’t see it very well.”

Johnson took advantage quickly, though, by changing his lineup.

“I was content to play a defensive game after that,” said Johnson, who had decided at halftime to make the change if the Bucks scored first.

Johnson was confident his team could hang on after taking the defensive posture in the game.

“The girls have been playing very well the last few games,” he said.

Goalkeeper Karrie Hoke backed up the Bucks’ defense by making 13 saves on 16 shots for the Golden Bucks, who improved to 7-5-2.

Brookes made three saves on four shots for MCI, who were eliminated with a 13-1-1 mark.

The Bucks will play a semifinal at Hermon at 3 p.m. Wednesday.

In EM Class C soccer quarterfinals Monday, the No. 3 Katahdin girls of Sherman Station defeated No. 6 George Stevens Academy of Blue Hill 2-0, and the No. 6 GSA boys upset No. 3 Calais 4-1.

Katahdin will next play at Schenck of East Millinocket in a Wednesday semifinal, while the GSA boys will host Fort Fairfield.

In EM field hockey quarterfinals, No. 3 Gardiner ripped No. 6 Nokomis of Newport 5-0 in Class A, No. 2 Belfast tipped No. 7 Hampden 2-1 after on the eighth penalty corner and No. 3 Oak Hill of Sabattus edged No. 6 Winslow 1-0 in Class B, and No. 2 Hall-Dale of Farmingdale topped No. 7 Boothbay 1-0 in Class C.

Among Wednesday’s semifinals, Gardiner will be at Skowhegan, Oak Hill will play at Belfast, and Hall-Dale will host Central of East Corinth.

Girls soccer

Katahdin 2, Geo. Stevens 0

At Sherman Station, the Cougars scored twice in the first half and then the defense preserved the win in the second half.

Jinger Dyer opened the scoring with an unassisted goal with 27:38 remaining in the first half, and Leslie Taylor scored with 10:10 remaining with assists from Jodi Dyer and Renae Landry.

Carrie Jo McNally made one save on two shots for the Cougars, now 8-3-2.

Eagles goalie Betsy Lepper stopped 14 of the 16 shots that Katahdin fired her way. GSA finished 6-6-3.

Boys soccer

GSA 4, Calais 1

At Calais, Scott Murphy scored a pair of goals and Derek Torrey added a goal and an assist, powering GSA to the upset.

Brock Mattson also scored for GSA (9-4-1). Kelsey Balombini-Goddard contributed an assist. James Inglis led the defense by making one save in net, facing four shots.

For 10-3 Calais, Eric MacDonald scored on a penalty kick. Matt Raye made 8 saves, facing 14 shots.

Field hockey

Class A

Gardiner 5, Nokomis 0

At Gardiner, Kelli Mason scored a pair of first-half goals to lead the host Tigers to victory.

Amanda Malinowski provided a goal and an assist for 13-1-1 Gardiner, while Kim Palmer and Chelley Choate added one goal each. Dawn Novy came up with three saves on three shots to post the Tigers’ 14th shutout in 15 outings.

Millie McDonald and Heather Deering combined to make 14 saves on 20 shots for Nokomis of Newport, which ended at 9-6.

Class B

Oak Hill 1, Winslow 0

At Wales, Lynne Gervais scored off an assist by Angela Castonguay with 3:46 remaining in the first half, giving Oak Hill the win.

Tracy Lamontagne backstopped the win with 15 saves on 18 shots for the 9-1-5 Raiders.

Jo Jo St. Peter made four saves on seven shots for Winslow, which finished at 10-5.

Class C

Hall-Dale 1, Boothbay 0

At Farmingdale, junior link Amanda Newton scored with 19 minutes left in the first half, converting an Abby Garofalo pass, to give host Hall-Dale the margin of victory.

Heidi Johnson made one save and faced three shots for the 9-1-3 Bulldogs.

Heather Reed had nine stops on 10 shots for 2-8-3 Boothbay Region.