Kilmarnock 1 Celtic 0:Robbie Keane's Celtic debut went spectacularly awry as Tony Mowbray's reign hit a new low with the club's first defeat to Kilmarnock in 32 meetings.
On-loan Tottenham striker Keane missed two golden opportunities to score in either half and he was upstaged shortly after the break by Chris Maguire, who celebrated his own debut with a fine winner for Killie in a 1-0 victory.
The result left Celtic 10 points behind Rangers, but now having played the same number of games, while also giving their opponents' survival hopes a massive shot in the arm.
A superb strike from Colin Healy gave strugglers Falkirk a welcome 1-0 win over lacklustre Aberdeen at Pittodrie.
The Irishman smashed the ball into the top corner on 31 minutes to give the Bairns a deserved win over the Dons, who offered little in attack.
Eddie May's side should have put the game beyond doubt but squandered a number of chances in the second half, however they held on for all three points to lift themselves off the bottom of the Clydesdale Bank Premier League table.
Billy Mehmet sent St Mirren into their first major final for 23 years as his stunning strike secured a deserved Scottish League Cup victory over Hearts at Fir Park.
The striker netted his seventh goal of the tournament in the 52nd minute when he curled into the top corner from 25 yards.
Saints were the better side for the majority of the game and survived some late pressure to book their first League Cup final appearance since 1956.
Selected Cross-Channel Results
Scottish Premier League
Aberdeen 0 Falkirk 1
Kilmarnock 1 Celtic 0
Scottish League Cup Semi-Final
Hearts 0 St Mirren 1
Premier League
Hull 1 Chelsea 1
FA Cup Fourth Round replay
Crystal Palace 3 Wolverhampton 1
Wigan 0 Notts County 2