don't change a winning team

If something is performing or functioning well enough, there's no need to change or interfere with it (as you may introduce new problems as a result.) A: "We don't really need to implement these ridiculous changes, do we? Our current method is working just fine." B: "Yeah, don't change a winning team." Why would they trade so many players in the offseason following a World Series appearance? Don't change a winning team, literally! Why are you fiddling with those cords back there? Everything's working just fine up here—don't change a winning team!