Mikel Arteta said Arsenal could not use their pre-season physical condition as an excuse for the 2-1 friendly defeat to Scottish outfit Hibernian.
Martin Boyle and Daniel Mackay put the Scottish side 2-0 up at Easter Road in Edinburgh, before Nicolas Pepe missed a penalty for Arsenal.
Emile Smith Rowe pulled a goal back in the 82nd minute but Arsenal could not find an equaliser, meaning their hopes of making a fast start ahead of the new campaign took a blow.
Asked whether a lack of training might explain the loss, Arteta said: "It does but there's no excuse because we want to come here and win the match.
"They worked really hard, the boys worked really hard and you could see that some of them were not in the best condition, but we're still very early in pre-season. It was great to see some of the young lads making their debuts here. We'll keep working."
Arteta's team finished eighth in the Premier League last season, meaning they missed out on a place in Europe for the upcoming campaign.
It means a blow to their income but Arsenal may benefit from having midweeks available for training rather than travelling, with Arteta still looking to impose his methods after a tough first full season in charge.
He brought his team to Scotland with the aim of getting not only physical tests under their belt but wins, alongside the training.
"Well I'm always disappointed when we lose a football match but it is the first game, we played with many kids and we only had four training sessions," Arteta said, quoted on Arsenal's official website.
"We've trained really hard and you could see that the players were a little bit leggy. I think we conceded the first goal, an accident, and the second goal was clearly offside. We created many, many chances but we didn't score.
"That's what pre-season is for, to take the things that we haven't done well into a training session and then improve."
Pepe's penalty miss came as a surprise, with Arsenal having been proficient from the spot over the 2020-21 season, converting all eight of their spot-kicks.
Pepe scored two of those, Pierre-Emerick Aubameyang also netted twice and Alexandre Lacazette converted four of four in the last campaign.