The hangover began to kick in at Broadwood Stadium as the cup conquerors of Celtic were vanquished 3-2 by the visiting St Johnstone side, which allowed Owen Coyle's men to leapfrog the Bully Wee in the First Division standings.
The Saints dominated the first half and should have taken the lead after 37 minutes when Paul Sheerin met a Ryan Stevenson cross, but the former Aberdeen player's shot cannoned off the post.
Sheerin had only three minutes to wait for his fortunes to turn. Clyde's Neil McGregor fouled Ryan Stevenson in the box with a needless tackle as the Saint was running away from goal.
Sheerin stepped up to slot the resultant penalty just past the grasp of the despairing Peter Cherrie.
A mere two minutes later and St Johnstone had doubled their lead. Trinidad and Tobago international Jason Scotland hared down the touchline, shrugging off Craig McKeown in the process, before cutting inside and slotting the ball under Cherrie from six yards.
Clyde failed to listen to Graham Roberts belligerent team talk at half-time and quickly found themselves three goals down. Sheerin curled a corner into the near post for club skipper Kevin James to head into the top corner.
The home side rolled their sleeves up and began to fight back with Craig Bryson and Tom Brighton in sensational form.
Midfielder Steven Masterton picked up a loose ball on the edge of the area and plumped to try his luck from 25 yards. The strike passed through a ruck of players, where Tom Brighton outstretched a toe to deflect the ball past a stranded Kevin Cuthbert after 55 minutes.
Brighton's second goal was one for the highlight reel as the striker latched onto a mis-kick from Eddie Malone to reel around and scissor-kick the ball into the roof of the net from eight yards.
The Bully Wee almost equalised in the 77th minute when Brighton was presented with a gilt-edged chance, but the striker scuffed his shot wide from only six yards when he really should have scored.