Blackpool prevailed thanks to an injury-time own goal from Barnsley's Scott Wiseman, while Darius Henderson exploited a stoppage-time error by Blackburn Rovers goalkeeper Jake Kean to earn Forest a first league win at Ewood Park since 1999.
Crystal Palace beat Watford 1-0 after extra time in the Championship play-off final at Wembley Stadium on Monday to secure a return to the Premier League for the first time in eight years.
Manchester United goalkeeper Tomasz Kuszczak has been loaned out to second-tier English club Watford for the rest of the season after falling out of favour with the English champions.
Harry Redknapp took his place on the Tottenham bench as his Premier League side squeezed past Watford 1-0 to advance to the last 16 of the FA Cup on Friday.