Roma coach Jose Mourinho has not missed the opportunity to attack Lazio coach Maurizio Sarri ahead of Sunday's Serie A capital derby.
The crisis began when Mourinho said Lazio had an added advantage over Roma as they would play on Tuesday in the Champions League against Feyenoord, while the Giallorossi would play Slavia Prague's Europa League clash on Thursday.
Sarri responded to the "special one" comments that Lazio were at war against Feyenoord, while Roma have a "friendly match" on Thursday.
The comment appears to have angered Mourinho, who opened fire on Sarri and reminded him of their difference in success in world football.
Speaking to the media, the Portuguese coach said: "I think this comment is not insulting to us, but to Slavia Prague, it seems to say that Prague do not have quality."
"I always respect my opponents, maybe that's the difference between a coach who won 26 championships and another who barely won anything, it's a mental difference."
"Every game has to be taken seriously, there are no friendlies."
Roma are seventh in the Serie A standings with 17 points, while Lazio are in tenth place with 16 points.