The Gunners fell to a 1-0 last-32 first-leg defeat in Belarus, with Alexandre Lacazette being sent off late on.
"It was certainly the worst performance we have seen under Emery," the former Arsenal defender told BT Sport.
"BATE, you have to give them credit, but Arsenal just didn’t have the penetration.
"There’s sloppiness within their play, you can blame the pitch, which is a poor excuse, but you’ve to be better than this if you’re an Arsenal team.
"On 70 minutes he made the changes, Arsenal then had even more possession. They’ve got it all to do now in the second leg. I do expect them to win that but it’s a poor performance from Arsenal."
Arsenal host BATE in the second leg next Thursday at the Emirates.
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