The emphatic 5-0 victory for the Polish champions, having been heavily criticised for only drawing 1-1 in the home leg in Warsaw, was a timely reminder that Legia are a cut above the average qualifying-round-unseeded fodder.
However, before anyone starts to afford them respect beyond their station, it is worth taking a peak beneath the surface of the club which can boast Artur Boruc among its former players and fanatical following.
Sure, Legia are the best team in Poland, by some distance.
But that's akin to being titled the best-dressed man in Albania, so far has Polish league football fallen.
And while Legia have more money than all the others they compete against for the title, they still can't afford to go out and spend seven figures on anyone.
Indeed, £500,000 is a stretch for them.
Which is why they are not to be found shopping in the major transfer markets. Rather, they scratch around for cheaper options in places like Cyprus, where clubs often struggle to pay wages when due.
Their major supply chain, however, is more locally produced.
Legia pluck the best from the other teams in and around them in Poland, reaping the double advantage of strengthening Henning Berg's side while weakening the opposition.
The former Blackburn, Manchester United and Rangers defender has not had an easy ride since taking over last year.
Winning the championship is not only expected, but a sacking offence if undelivered.
Getting Legia Warsaw into European competition - preferably the premier competition for the first time since 1996 - is what is used as the real measure of the manager, and what their vociferous and passionate support believe should be an annual rite of passage for a team with their history.
Spot anything familiar in all of this?
Unlike Celtic, however, Legia are not in a strong financial position, their turnover around a fifth of that enjoyed by the Parkhead club.
When their previous owners, the ITI Group, sold out to the chief executive, Boguslaw Lesnodorski, and his business partner Dariusz Mioduski, it was ostensibly at a knock-down price with inheriting the club's debts the real cost involved in the deal.
IN December, Berg had been brought in, his CV not the strongest, but his Manchester United connection - and, in particular, the suggestion he had a hot line to Sir Alex Ferguson - considered a definite attribute in the wide eyes of his new employers.
The style being adopted, and the performances delivered, have not convinced many Berg is the man to take Legia to the next level.
Lifting the championship last season bought him some time.
But, after the disappointing draw with St Pat's - they needed an injury-time goal from old warhorse, Miroslav Radovic to avoid defeat - the knives were out and being sharpened for a quick kill if Legia crashed out in Dublin on Wednesday.
The pressure was only increased when the draw for the third qualifying round raised the strong possibility Celtic would await the winners, a match-up the excitable Legia fans relished.
One of the biggest criticisms about Berg's management style has been his penchant for chopping and changing his starting XI, viewed as betraying a weakness in a man who does not know his best team.
In Dublin, in front of Ronny Deila, John Collins and Celtic's major shareholder, Dermot Desmond, Berg went back to what is considered his top team.
The result was an easy victory as St Pat's suffered a late collapse which saw them go from a goal down with 21 minutes remaining to a 5-0 thumping by time up.
Two goals from Radovic - now playing as the main goal getter in lieu of a genuine front man - and singles by rising star Michal Zyro and striker Marek Saganowski, plus an own goal from Conan Byrne sounds impressive.
But, like Celtic's win over KR Reykjavik at Murrayfield, the quality of their part-time opposition has to be taken into account.
Even though he left long before the end of the game in Dublin, Deila undoubtedly spotted how much Legia rely on Radovic.
At 30, the wily Serbian's old head is a potent weapon, but his equally old legs mean he can be tracked and shut down.
Achieve this, and Legia struggle - badly.
Ahead of him, Berg has gone back to playing 36-year-old Saganowski as the front-line leader.
The Legia fans love his whole-hearted commitment, but even they can't overlook his lack of genuine quality.
CELTIC'S main weakness under the high-tempo, attacking style Deila is demanding they play is their susceptibility to a quick counter-attack.
But pace is not one of Saganowski or Legia's strengths, and with Virgil van Dick and Efe Ambrose quick across the ground, they could struggle to make turnovers count.
They do have some speed, in the wide areas, where former Motherwell player, Henrik Ojamaa, is among those vying for a position.
But the speed they do have is not matched by quality or technical ability to hurt well-organised defences.
The failure of main wide-man Jakub Kosecki to regain his best form after injury problems is hurting them badly.
At 21, Zyro is held up as the next big thing.
But while he is certainly tall, he takes a while to move his rangy frame across the surface.
And upstairs, where game intelligence is processed, those who watch the club regularly do not consider things happen too quickly, either.
So the main thrust now comes through Radovic, with the vision to create chances created by the Slovakian midfielder Ondrej Duda.