THIS time it's personal. Neil Lennon avoided saying as much in the build-up to his side's fixture against Cluj on Thursday night, but you'd be hard pushed to find a Celtic supporter who doesn't think that the European rematch is anything other than a revenge mission.

After the disastrous defeat to Dan Petrescu's side in the Champions League qualifiers - Celtic's only defeat this campaign so far - the Parkhead crowd will be desperate for a win over their Romanian opponents. And if they can get a few goals on the way then all the better.

The problem, though, is that this gung-ho attitude is precisely what caused Lennon's side problems in that fateful game and ultimately resulted in their elimination from the Champions League. On three seperate occasions, Celtic had the advantage in the tie and were heading through, yet the Scottish champions contrived to lose anyway.

So, what are the lessons that Lennon should have learned from the match?

Most pertinently, the main takeaway from the 4-3 defeat to Cluj in August was the complete lack of control that the home side, particularly in midfield, had in proceedings. When Celtic should have been dropping the tempo and maintaining possession, they instead charged up the pitch looking for just one more goal that would settle the tie as a contest. It never arrived, and Celtic paid the price.

READ MORE: How can Rangers beat Young Boys in the Europa League?

The graphic above details Celtic's average passing statistics in all competitions this season and the numbers that Celtic posted in the second leg against Cluj, and a few things are noticable. Firstly, that both the overall number of passes - and their accuracy - took fairly significant dips. This is to be expected, though, given the higher calibre of opponent that Celtic were facing.

However, what is concerning is the average number of passes per possession that Celtic posted that night. Lennon's team usually manage around six successful passes before they lose the ball; against Cluj, that figure dropped to 3.8. Additionally around 7% of Celtic's passes under Lennon this season tend to be long and against Cluj, that figure rose to just over 10%.

These figures may seem small or insignificant, but they are informative of what went wrong in the Champions League qualifier. Celtic struggled to maintain possession and spent too much of their time simply lumping it forward in hope. There is no question that out of the two sets of players, Celtic have the superior technical ability so the pragmatic thing to do on Lennon's part would be to make the most of this clear advantage. Celtic didn't, and they lost.

Up front, there weren't too many issues - after all, Celtic did score three goals, which should have been more than enough to see them qualify for the play-off. But at the back, a few players decided to have an off-night that simply cannot happen again. To be fair to Cluj, their forwards were particularly clinical on the night (all nine of their shots were on target) but that does not excuse the below-par performance from Lennon's defence.

READ MORE: Scottish Premiership Manager Power Rankings: Week 7

Celtic's xG against more than doubled that night, they conceded more shots than they usually do and Lennon's side contested - and won - significantly fewer defensive duels than they usually do. There were mitigating factors at play; Callum McGregor at left-back, poor goalkeeping from Scott Bain, Scott Brown's hand-ball, but the fact remains that Celtic put in arguably their worst defensive showing since Lennon was re-appointed in the 4-3 defeat.

The Celtic defence looks far more settled now and it's hard to imagine that Boli Bolingoli and Christopher Jullien - both of whom missed the first leg - won't start this time around. A string of individual errors ultimately led to the goals that the visitors scored back in August but there was no point where the home side's defence looked remotely resolute. This time, that should be different.

The most important thing for Lennon on Thursday night - and the most crucial lesson to be learned - is that the Celtic boss must resist the temptation to play an attacking brand of football that places little or no emphasis on controlling the ball or maintaining possession. The lack of control, especially in midfield, led to a chaoitic match that played into Petrescu's hands. Celtic have the better, more technical players and it's this asset that Lennon should exploit on Thursday evening.

The home crowd will undoubtedly urge the players forward, to go for the oppositon's throat, to exact some form of revenge on the Romanians. It's Lennon's job to ensure his players keep their cool, play to their strengths and remain composed. Celtic have tried going for the jugular against Cluj before and it hasn't worked: on Thursday night, we'll see if they've learned their lesson.