Gala won 1-0 thanks Victor Osimhen's successful penalty.
Afterwards, Slot said of Liverpool's performance: "Disappointing because you play football to win a game and that’s what we didn’t do. For me it was a different loss to the one we had against (Crystal) Palace because for me there was a lot more to like, especially in the first half, which was maybe different to the Palace game.
"And in the second half, it became harder and harder for us to create. First of all, because they were fighting with all they had so you have to give credit to them and second of all because we hardly played in the second half. By ‘hardly played’ I mean the ball was hardly in play."
The Dutchman also said: "It’s difficult. There can be so many reasons why an individual makes an error pass or a mistake. What you see is, and I think I explained this many times, is that there are a few players from us that missed pre-season so you simply cannot play them every single (game). Well, you can but then that could become a risk of players becoming injured.
"We have seen this more and more because the demands go up more and more and if the demands go up you have to prepare players for these demands. That means it is not always that I want to rotate but sometimes I need to because a player is not ready to play three times 90 minutes in seven or eight days."
Squad depth
Slot also insisted: "I like my squad so much but we don’t have 25 or 26 (players), so if we end up with two, three or four injuries, 15 or 16 players, where Rio (Ngumoha) and Trey (Nyoni) are two of these 15 or 16, need to play almost all the minutes and then things can become complicated.
"But this is a decision we have made together, I completely believe in this, because if you have 25 it’s very hard to manage your squad. But as a result of that, with Hugo, Alex (Isak), Conor (Bradley) and (Alexis) Mac Allister not having the pre-season a player should have, that also results in the fact that I cannot play them every time."