Sagna, 29, had only recently returned to action after suffering a fractured fibula in a game against Tottenham last October.
"It is a broken fibula, the same leg," Wenger said. "He was kicked on it, it has not happened alone. When he was kicked, he has broken the leg. The guy closed him down and walked on him. I don't know if it was deliberate or not."
The defender's latest leg break occurred in the same area as his previous injury. Sagna was stretchered off in the first half of Arsenal's draw with Norwich at the Emirates Stadium today.