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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Sunny spells continuing to develop into this evening. Dry with mostly clear skies overnight, before a sunny but chilly start tomorrow
Dry with sunny spells into this evening. Turning chilly with clear spells overnight with a sunny but cold start tomorrow
Dry with an increasing amount of bright spells this afternoon but feeling cool