Maybe, but I have not experienced this in my matches. The last 14 weekends, my association has a 27-1 record, if associations results were really random I think we would have lost more than once in 14 weeks.
What I think is happening is the game engine favors athleticism over technical skills. So those managers with lower athletic skills (fitness, speed and strength) have greater odds of being upset than one with an advantage in those skills.