Mikel Arteta said his Arsenal players were "fuming" after defensive errors saw them fall to a 3-1 preseason defeat to Real Betis in Dublin on Wednesday.
The Gunners went behind early to goals from Rodrigo Riquelme and Nelson Deossa before pulling one back through Piero Hincapié.
But they would go in at halftime already 3-1 down after Pablo Fornals added a third shortly before the break.
Asked about what the mood in the dressing room was like during the interval, Arteta told reporters: "Very upset, given a hard time. They are fuming, but this is good. That's what we need."
The Arsenal boss named a starting lineup unchanged from the one which beat Girona 4-1 on Friday, which meant that the likes of Kai Havertz, Viktor Gyökeres and new signing Christos Tzolis all started.
But Arteta made a raft of changes throughout the game, including giving defender Gabriel his first minutes since Brazil's World Cup round-of-16 defeat to Norway.
Arsenal found themselves a goal down in the ninth minute when goalkeeper Kepa Arrizabalaga failed to make contact with a corner and Riquelme lashed home at the back post.
Tzolis failed to take advantage for Arsenal when Betis goalkeeper Álvaro Valles passed the ball straight to the Gunners' summer signing before Deossa put the visitors 2-0 up with a 30-yard thunderbolt into the top corner.
Arsenal reduced the deficit when Valles misjudged a corner from Tzolis for Hincapie to head home, but Betis restored their two-goal advantage before the break as former West Ham midfielder Fornals swept the ball beyond a stationary Kepa following Havertz's misplaced pass.
Arteta's wholesale changes at halftime saw the game lose its momentum, with neither side creating another clear-cut scoring chance.
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"Well, the important part is to win it and we didn't manage to win it, so disappointed obviously for the result," Arteta said. "It's true we used 25 players, so you need to give a bit of context to the game.
"In the first half, with more starters, two very different things: how we played and how we competed, because we had some fantastic moments in the time we played.
"The way we competed especially in and around our box in a number of standards that we are used to, so there are things to improve obviously, some positives to take from the game and then a bad result sometimes it's good to create even more fire in the belly."
Information from PA contributed to this report.
