The Gunners battled to a 1-0 win at Old Trafford on Sunday (17.08.25) and Saka acknowledged that the team will have to be better in future games.
The forward said: "It was not a great performance. We are happy with the three points, to come away from Old Trafford with a win.
"We were not up to our usual standards, the basics, sloppy giveaways. Our decision making was not great and that cost us and gave United a lot of momentum. We did not get punished for it but we cannot do it every game."
Arsenal's new striker Viktor Gyokeres had a quiet Premier League debut but Saka was "impressed" with the arrival from Sporting Lisbon despite his lack of goal threat.
The England international said: "I was impressed with him and he battled for us. It was tough. There was a big battle up there.
"I thought he did well. His performance gives us something to build on and I am sure it will help him next week. He has slotted in well and so have the other guys."
The Gunners are looking for a first Premier League title since 2004 after finishing as runners-up in the past three campaigns and Arteta has urged his team to keep "digging" in their pursuit of the prize.
The coach said: "You keep digging, digging, Âdigging and you have to be digging because one day the gold is going to be there. That’s all the time. When I’ve been taught, when I’ve been educated, that’s it.
"For three seasons we’ve had more points than any other team in this league (Manchester City have accumulated more), which is incredible. That’s how you have all the consistency. Now we have to do it in a season to have one more point or the same amount of points and more goals different than any other team. That’s the objective."