In terms of enthusiasm, it would be absolutely devastating so that would seriously affect any games played after those 2. If you have enthusiasm of, say, 8 before the games, chances are you would end up with an enthusiasm of 1 or 2 afterwards (I've never been down that low before so I can't say for certain), meaning that your players would have essentially played themselves to death mentally and physically and would seriously underperform in any games afterwards.
Of course, if you were looking to do that in your playoff games, the long term effect wouldn't be too bad because all teams' enthusiasm is reset to 5 for the new season.