The Senegalese striker, who has made two substitute appearances for Saints since arriving on loan from Fiorentina, suffered an ankle knock playing for the reserves this week.
Veteran full-back Graeme Murty (knee) and young winger Kayne McLaggon (Achilles) are making progress but are not ready to be considered.
Midfielder Jake Thomson is still on international duty with the Trinidad & Tobago Under-20 squad.
Manager Alan Pardew could therefore name the same starting line-up which secured Saints' first win of the season against Yeovil last weekend.
Pardew is also considering naming an outfield captain as he feels current skipper Kelvin Davis cannot influence matters as much from in goal.