There is nothing quite like seeing your opponents live, and I am sure Ronny will have learned a lot about the Polish champions.
I reckon Legia will be the toughest side Celtic have met in any of their qualifiers or play-offs in the past few seasons.
They have had money ploughed into their team, and Henning Berg will have made the Group Stage a priority.
One thing for sure is that they will be significantly better than KR Reykjavik, who showed on Tuesday that they were simply no match for Celtic once the Bhoys got going.
The ring rust which was evident in the first leg in Iceland had gone, and the scoreline reflected the gulf between the teams.
It could have been much greater.
It was the same with Legia. They did not do themselves justice in their first leg against St Pat's, but stepped it up to blow their opponents away in the second game.
The Celtic fans would have preferred a trip to Dublin next Wednesday, but it is now Warsaw, and they can look forward to sampling a very partisan atmosphere.
That should not be a problem for the players. They have just got to focus on continuing the improvement they have been showing with every 90 minutes that they play.
The one concern might be the games against St Pauli tomorrow and Spurs in Helsinki next Saturday.
I reckon Ronny will use his fringe players in Germany.
But, they could be under contract to field a strong side against Spurs, even though it comes between the two matches against Legia.
I have heard it suggested that the pressure is off because, even if they are knocked out at this stage, they parachute into the play-offs for the Europa League. I can't go along with that. If you start to think that way, you leave yourself open to a bloody nose.
It's got to be Champions League. Nothing else will satisfy. But, the draw has done them no favours in this round, and it is going to be tough.