Aubameyang became Arsenal's record signing when he joined from Dortmund for £56million in the January transfer window but he has cut a dejected figure on the pitch and has been deprived of regular service.
Smith told Sky Sports: "He looked a shadow of the player he was at Dortmund.
"Even he, in the short time he's been at Arsenal, has been affected by the mood.
"He got his goal with a little flick, but he's not the player I hoped he would be.
"I'm not saying he's a bad player, but it's a malaise through the dressing room and he's been affected."
"We haven't seen anything from Mkhitaryan in an Arsenal shirt yet and this is when you need your big players, in an attacking sense, to get you back into a game.
"I always think with Arsenal that when they concede the first goal, like they did, then they lose their heads a little bit.
"They can't just go back into their shape and keep it tight for 10 or 15 minutes and work their way back into a game."