Forest were chasing a club record-equalling seventh straight win but it looked like manager Billy Davies would taste defeat for the first time in eight games when Will Buckley put the visitors back in front with five minutes remaining.
Poyet though had sympathy for the goalkeeper and said: "To begin with I thought the shot must have taken a deflection but when I've seen it again I nearly killed myself!
When you are a keeper you pay the price and Casper has done that today. He was having a very, very good game, making two or three good saves, coming for crosses and kicking very well.
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After a dry start, sunshine will become increasingly hazy as cloud thickens, bringing patchy light rain to some parts.
After a dry and bright start across the region, sunshine will become increasingly hazy as cloud thickens.
Showers soon dying out this evening to give a dry night with some long clear spells and light winds.