Thanks for responding. Sorry to ask but I really don't understand why a level 30 team play twice with a level 50 team because I assume you are talking about league levels. Do you actually mean current overall average quality of your team is 50?
As you did not provide much information like screen shots, it is hard to discuss specifically about your case. One possible reason is that your opponent is competitive because they have high quality starters and low quality backup players.
I understand that managers of strong teams feel bad for losing matches against weak teams. But from angle of weak teams, victories may not be results of pure luck but good pre-match preparations, in-match changes, etc.
My teams have some winning records against very strong teams. Generally, in these situation, my strategy is using very defensive tactics, keeping scoring low, keeping patient and defensive during the match even if my team is trailed up to 2 goals, and probably turning to attacking near the end of the match. I never sit down and wait for losing. I will at least give those strong teams trouble during the match.