Rockingham-Mandurah have gone down to University in a two-day Premier League clash at Lark Hill at the weekend.
The Mariners were chasing 273 runs on Saturday.
They lost two wickets early before a promising innings from opener Brandon Jacobs who top scored with 71 runs.
The wickets soon kept falling though and Rockingham-Mandurah were bowled out for 178.
The Mariners are up against South Perth at Richardson Park in another two-day game this weekend.
"Should be a real contest, a big challenge for our boys," Coach Kris Kennedy said.
"South Perth have had a tough start to the season and will be really pushing to make amends.
"We’ll need to have a big emphasis on our consistency and being patient in building partnerships.
"If we can execute the basics it will give ourselves an opportunity to set the game up."