THIS was not so much a hangover caused by Europe but a self-inflicted headache that arrived all of a sudden.

And in the moments when Blues were so fuzzy, a vibrant Southampton side profited and had the game in the bag just after the half-hour mark passed.

Blues pulled themselves together in the second half and might have made the Saints jittery had Stephen Carr’s shot not hit the post after Chris Wood scored.

But Richard Chaplow sneaked through with 12 minutes to go to put the gloss on a deserved Southampton victory that took them to the top of the Championship.

Chris Hughton had rested key personnel on Thursday, when Blues played SC Braga in the Europa League, and they all returned here.

And a misjudgment by one of that number, Steven Caldwell, in conceding a game-changing penalty, proved significant and precipitated a truly wretched spell by Blues when the damage was done.

In fairness, Caldwell hardly executed a blatant wrestling move on Rickie Lambert and Hughton described the decision to award the spot-kick as ‘soft’.

But it’s always a risk to entangle your arms around someone when marking.

The game started amid a torrential downpour at St Mary’s and initially there were suggestions Blues were going to rain on Southampton’s parade.

They began very sprightly and Jean Beausejour caused panic on the left by getting in a couple of good, low crosses.

Jonathan Spector fired wide after Marlon King set him up and from an eighth-minute free-kick, as Blues continued to ask questions, Kelvin Davis made a smart, low save from a powerful shot by Wood, which was deflected on its way through.

But from the moment Caldwell was penalised, a Blues implosion began.

Caldwell got hold of Lambert’s waist as they jostled for position at a left-wing corner and the burly striker went over.

Lambert composed himself to smack the ball to the left and it screwed in off the base of the post.