Former Arsenal full-back Nuno Tavares decided to leave the Stadio Olimpico at half-time after being substituted during the Rome derby, and could now face a fine from his new club Lazio.
The 25-year-old was trusted to start the fiery derby after making a permanent switch to the Italian side from Arsenal in the summer, following a one-year loan spell.
But the defender had 45 minutes to forget as he was at fault for what proved to be the winning goal for Roma, scored by Lorenzo Pellegrini.
Tavares got caught on the ball on the edge of his own box seven minutes before the break, and moments later, Pellegrini was wheeling away in celebration after sticking the ball in the back of the net.