Saka was forced off during victory at Crystal Palace on Saturday and it's since emerged he faces being sidelined for four-to-six weeks.
Arteta said ahead of their clash with Ipswich Town, "It’s not looking good. He’s going to be out for many weeks.
"I cannot be too specific because I don’t know, but it will be many weeks.
"Yes it’s a huge one. Obviously he’s a big player for us. You just have to see the impact that he has on the team, but it’s going to be a really good exercise for all of us to think about ways to overcome another challenge, because we’ve already had a lot in the season.
"It’s part of the development of a player. At some stage, at this level, you are going to get injured – unfortunately badly. It could have been worse, it could have been something else that can take you out for a year. It’s how you react to that, how you overcome that situation. It’s a great learning process for him as well. It is what it is, he’s injured, we cannot change it. How are we going to use this time now to help him for the following years in his career?"
On how Saka has taken the news, Arteta also stated: "He was gutted. You can tell that he's not been injured because he was really, really emotional. He was really down and we need to lift him up because it's part of what we do. It's part of what he does. It's part of his job, big part of his job, he will be fine, but I think he's going to need a few days.
"He's going to immediately realize that he's so important in that dressing room. So his energy level, his body language, the way he communicates with the rest of the team has to be really, really good because it's the only way at the moment that he can help. So he better do that well."