Gibbs suffered a fractured metatarsal in his left foot after a lunge by Standard Liege's Eliaquim Mangala.
It came just eight days after he hurt his right foot playing for England Under-21s.
Wenger snapped: "Gibbs is much more serious. He has a big hole in his leg.
"It was a very bad challenge from the No 22 and it was not his first try. Unfortunately he doesn't look too good. The vibes from the medical team were not very positive."