Giuseppe Rossi has battled back from a cruciate knee ligament to return to action, but he received mocking chants as he played against the side he suffered the injury against.
The former Manchester United man was leading the Serie A scoring chart when he sustained the injury in January playing against Livorno.
At first it was feared that Rossi may be ruled out of the World Cup, but he returned to action ahead of schedule and will make the plane for Brazil.
However, the Livorno fans were brutal in their response to Rossi when Fiorentina visited the Stadio Armando Picchi.
Some Livorno supporters chanted for Leandro Rinaudo, the man who injured Rossi last time, to crack his knee again while others demanded that Rossi make the trip to Brazil in a wheelchair.
Lynn and Rossi had the last laugh as Fiorentina triumphed 1-0, sentencing their Tuscan rivals to relegation to Serie B.
The goal came from in-demand winger Juan Cuadrado who is said to be a target for Manchester United, Arsenal, Bayern Munich and Barcelona.