A mysterious sketch of an Infiniti four-door coupe has surfaced online. Speculation suggests it could preview the long-rumored flagship sedan.

Autoblog has managed to obtain a mysterious sketch which shows an Infiniti four-door coupe.

Little is known about the sketch but it was penned by Alfonso Albaisa who was recently appointed as the brand's executive design director. It shows a stylish sedan with a prominent grille, muscular rear fenders and a crescent-shaped C-pillar. We can also see an aggressive front bumper and massive alloy wheels.

There's no telling if the sketch is just a design exercise or something more but previous reports have indicated the company's flagship sedan would be a four-door coupe with a turbocharged V6 engine.

Gallery: Mysterious Infiniti four-door coupe sketch surfaces online