The Morris Mavericks and Miller Aces won their Zone 4 High School League semifinal openers Monday night.

Mavericks 5 Thunder 1
Justin Keck scored three times as the Mavericks defeated the defending champion Morden Thunder 5-1 in game one of their best-of-three semifinal. Max Collette had the other two goals for the hometown Mavericks. Derek Wiebe replied for Morden. Morris goaltender Ryan Columbe made 29 saves. Thunder netminder Owen Domitruk faced 50 shots. Game two goes Wednesday (7:30 p.m.) in Morden.

Aces 8 Tigers 1
Rory Penner, Andrew Dyck and Parker Sawatzky had two goals each in the Aces 8-1 victory over the Pembina Tigers in game one of their semifinal in Altona. Colton Harder and Kirby Sawatzky also scored for the Aces who led 4-0 after the first period. Allister McNab had the lone goal for the Tigers. Miller goaltender Declan Enns stopped 20 shots. Pembina netminder Nathaniel Degraeve faced 47 shots. Game two goes Wednesday (7:30 p.m.) in Manitou.