The performance was hailed by PSV coach Eric Gerets, who claimed O'Leary's side showed just how a European away game should be played.

Gerets also described Leeds' organisation as "perfect", and that was mainly due to the displays of United's 'bad-boy' triumvirate of Smith, Mills and Bowyer.

Smith has now completed his five-match ban, but for the other two it will be back to watching from the sidelines again this weekend when Leeds travel to Everton in the Premiership.

But at Elland Road against PSV, with all three players benefiting from basking in the European spotlight last Thursday, O'Leary reckons they could prove the difference between success and failure.

"We've been missing an edge for various reasons this season, although I did make people aware this was going to be a very difficult one, particularly with what we were going to have to deal with off the field," said O'Leary.

"You have a squad to cope with injuries, loss of form and suspensions, but we've had all of them rolled into one. We've expended too much energy into matters off the field.

"You have to have the players you want out there on a regular basis, but we've not had that in any way, with Bowyer, Mills and Smith all self-inflicted.

"Hopefully they will have learnt their lessons from this season because they've sat and watched too many games instead of playing for us.

"But having them available last week made a difference to us, without a doubt. It gave us a better balance and improved us.

"They should now be better for playing, while they've trained well since that game and that too will make a difference for us."