Following a nervy first half Mainz took the lead in curious circumstances when they were given a penalty by Video Assistant Referee system VAR after the referee had already blown for half-time.
In the 45th minute, Freiburg's Marc-Oliver Kempf handled a shot from Daniel Brosinski in the six-yard box.
Referee Guido Winkmann ignored the appeals, blew for half time and made his way towards the tunnel along with both sets of players.
Mainz 05 and Freiburg's players are forced to cut their half-time interval short after VAR awards a penalty during the break.
Freiburg coach Christian Streich, who was recently sent off for dissent in a league match, was pictured on the sideline smiling and shaking his head in disbelief after being told to bring his players back out. One Freiburg player could even be heard saying: "No, we're not coming back out".More news: $1.76 EPS Expected for Domino's Pizza, Inc
Pablo De Blasis kept his cool from 12 yards to give Mainz the lead.
The 2-0 win sees Mainz leapfrog Freiburg in the Bundesliga table on goal difference, climbing out of the relegation zone at the expense of their defeated opponents.
The game itself may have been otherwise unremarkable, but that didn't stop the fans from creating a spectacle of their own as they continued to display their displeasure with Monday night games.
Finally, in the seventh minute of added time, De Blasis converted the penalty.
But, as it turned out the home supporters were in fact protesting against Bundesliga fixtures being played on Monday nights.