THERE will be a full house when Neil Lennon and Gordon Strachan sit down for a fans' event in one of the suites at Parkhead later this month, and an enjoyable night is pretty much guaranteed for the supporters who buy tickets for a question-and-answer session with the charismatic Celtic managers past and present.

Whatever topics are discussed, though, and however entertaining and sparky the chat becomes, it will never be as significant to Celtic as the private conversation which took place between those two men in a phone call four years ago.

It was the call which set Lennon on his way to managing Celtic. Strachan was in charge at the time and it was on an evening when he was doing some punditry work for Sky Sports, covering a European tie, that he took a moment to phone Lennon and offer him a coaching role. Lennon had left Celtic only a few months earlier to wind down his playing career with Nottingham Forest and then Wycombe Wanderers.

Today it seems natural that Lennon would gravitate back to Celtic as a coach or manager, but at the time the call was entirely unexpected. At Lennoxtown yesterday, for his usual pre-match media briefing ahead of tomorrow's SPL game at Dundee United, he reflected on Strachan's invitation. He would not be the manager nor the man he is now, he admitted, had he not answered the call. "I wouldn't think so. You never know. Your life changes overnight. There are opportunities that come and go, you look back on a lot of things, but I am sure that was a step in me being where I am now.

"I think Gordon was doing a European game for Sky and, either before it or after it, he gave me a call and said: 'look we could do with a hand up here, do you fancy helping out?' I was just ticking along seeing out my career with Wycombe, helping Paul Lambert [their manager at the time] a little bit. And then the opportunity came along under hugely emotional circumstances to come back to Celtic and I just felt it was too good an opportunity to turn down."

Strachan had a coaching vacancy because of the death of Tommy Burns. In turning to Lennon he replaced one iconic Celtic figure with another. When Strachan left in 2009 Lennon considered leaving too – figuring that new manager Tony Mowbray would want only his own men in the backroom staff – but chief executive Peter Lawwell talked him into staying. He took a role with the "development squad", younger players on the edge of breaking through, and rolled up his sleeves.

"That was a great year for me in terms of making mistakes, bringing on younger players and doing the dirty bits of the job. We travelled everywhere to play games, from Blackburn to Barrow, Cork and Derry. It was great and gave the young lads a taste of what it would be like to travel with the first team. I learned a lot in that year and then when Tony Mowbray left I had the opportunity to take this job [as caretaker] and I felt 'you have to grab it and see where it takes you.' It has taken me a long way in a short space of time."

Two years later, he has won a league title and a Scottish Cup as manager and his team is in a handsome position in Group G of the Champions League. The inclination to mentally leapfrog the United game and think about next Wednesday – when Barcelona come to Parkhead – was there for the media yesterday as it may be for his players tomorrow, but Lennon himself would only consider Tannadice.

"I don't want to talk about Barca today. The SPL is our priority and with the players being part of a new adventure in the Champions League there are times when they get distracted. I felt that was again the case at the weekend when they didn't turn up [during the 2-0 home defeat to Kilmarnock]. I don't want people to 'save themselves' or rest themselves for Barcelona because that is just one game and the season doesn't end on November 7. There are more big games to come. Barcelona is a big game, but one of many."

Tannadice is one of Lennon's favourite grounds. He likes the colour and the atmosphere of the place and has a good record there as player and manager, albeit United won the most recent meeting there, 1-0, in May. Scott Brown, Georgios Samaras and James Forrest are doubts for Celtic while Lassad is out. Lennon will ask Craig Levein – if he is still in his job – to omit Brown from the Luxembourg friendly later this month, although in general he is upbeat about his captain's degenerative hip condition. The problem is helped by rest.

"Ideally, I would like him to be left out of that because we have a heavy schedule of games," said Lennon. "I think if there is an opportunity for him to have a break then we will be asking for that. I hope he's fit [for Sunday] because he's playing brilliantly. He's playing the best football of his career at the minute and it's a question of him and ourselves managing him through this."

n Tickets for the Lennon and Strachan Q&A on November 24 cost £75 and are available from the Celtic sales team on 0141 551 4311/4314/4316.