They didn't play as usual because they didn't use their best lineup. There were some key players on the bench, Liverpool seems a bit underestimate Toulouse. I can understand if Klopp used some substituted players, he didn't see Toulouse to have a chance to steal points. It is a small team, they don't have many quality players and they are not in their best form in Ligue 1. However, it is a mistake to underestimate any team in Europa League, this competition often gave us a big surprise. Klopp didn't learn much from previous history in Europa League. Although the defeat won't impact a big thing for the chance of Liverpool to qualify to the next round, but the fans must feel unsatisfied with Liverpool game. Also, the players may drop their mentality due to the defeat from a smaller team.
Well, I hope Klopp will be more careful to choose players for the starting lineup in the next match. He must realize that he needs to keep the wins, it will keep the motivation of all players. He also must order all the players to keep playing with high intensity and be more aggressive. Liverpool players should never underestimate any team, specifically for the teams in Europa League.
Little teams matter a lot especially to the team spirit and in a competition across Europe, I think no team should be considered small, though the defeat might not have much effect on the log leaders, Liverpool but also they have to know the fans and bookies are in their favour and should maintain the winning streak for a long period of time.
I think switching line ups isn't a bad idea but it should be done with caution and I hope Klopp has gotten a cue from this defeat and will bounce back to winning ways over the weekend, Liverpool are a very good side to watch, let's see how the weekend turns out for the team, they'll be playing against Brentford in their Domestic league game on Sunday at Anfield and that's should be an easy game for them.