Havertz will undergo surgery in the next few days and is likely to return ahead of the 2025-26 campaign.
"He was going to stop a shot after a set piece and stretched the leg and he felt his hamstring," Arteta said. "We were having a great camp in Dubai, recharging, training, having some time off and connecting again with nature and a different environment. And then the injury happened in a very unexpected way, certainly. So it's a big blow, obviously, because of the injuries that we have. Yeah, he was going to stop a shot after a set piece and stretch the leg and he felt his hamstring."
Despite the latest setback, Arteta admitted his team must adapt their playing style, adding: "There are certain things that we're going to have to adapt and again, it brings another opportunity as well because you're going to have in the front line players that are very unpredictable, so good in one-vones, very creative, very sharp and it's going to give different headaches as well to the opposition."