Mjallby: Transformation (StuForster/Allsport)

The Swedish stopper has been a rock in a team which has leaked only 24 league goals this campaign. His displays, and those of his defensive colleagues, are not recognisable from those which heaped personal embarrassment upon Mjallby only a year ago.

He said: 'I always believed that we had a good place here but the tactics weren't there last season, especially defensively. We were not strong enough and were running around like headless chickens.

'You have to look to yourself and say: "I did not play well enough". But it is hard when the team isn't working properly and not playing well because we don't have tactics.'

Mjallby can trace the transformation back to pre-season work in Denmark after former Celtic striker Harald Brattbakk scored twice for FC Copenhagen in a friendly. Olivier Tebily and Rafael Scheidt - two John Barnes signings - teamed up in central defence for an appalling display that evening. O'Neill then switched to a three-man operation at the back, which was to include shifting Mjallby from a midfield role.

'I think sorting the defence was one of the first things the manager did,' said Mjallby. 'Now, we don't have to be too fancy at the back.

'We do our stuff and defend properly, leaving it to the more skilled players to take it from there. This is the first season in which I have felt comfortable at the back.

'I think he looked at the pre-season games where we conceded too many stupid goals, as we did in Copenhagen and for the whole of last season.

'I think he tried to put in three strong central defenders, like he did at Leicester, and it has worked out. I think we've been quite solid in defence. I honestly didn't think we'd get to the stage where we'd turn the 21 points behind Rangers around so much.

'I don't think either that the manager knew too much about the squad in pre-season. But what he did bring in straight away was a good mentality. We are very strong mentally.'

Meanwhile, Mjallby has confirmed his commitment to Celtic by declaring an intention to miss two Sweden games in June.

He requires a pelvic operation but wants to have surgery immediately after the end of the Scottish season. Missing the World Cup qualifiers against Slovakia and Azerbaijan would give him the best chance of being fully fit for pre-season ahead of Celtic's Champions League campaign.

He said: 'I would rather wait until after the Scottish Cup Final. There are two Swedish games but I don't see myself being involved in them.

'I need a rest and if I was to play in those two then I might not be fit again by the time the new season starts. The main priority is to be right for starting to play again for Celtic.'