Goran Popov's spitting incident had a big influence on defeat to Tottenham yesterday.
Reid lamented on the WBA website: "In recent weeks we've been shooting ourselves in the foot by going one and two down which makes it difficult.
"Yesterday, at the start of the second half, Goran's let us down with the red card. He's apologised and he's let us down, so what more can I say?
"He's got a suspension now and we've got Ridgey [Liam Ridgewell] to come in and fill that gap.
"I can't stress how difficult it is when you go down to ten men.
"It's just a moment of madness and it happens in football - but as I say we can't keep shooting ourselves in the foot like that.
"We need to give ourselves a better opportunity to stay in the game."