Arteta’s players, pushing for Champions League football, didn’t lay a glove on their hosts at St James’s Park, where a strike from Bruno Guimaraes and a Ben White own goal gave Eddie Howe’s side a 2-0 win.
“Really tough night,” said Arteta. “Newcastle were 100 times better than us in every department from beginning to end. It’s very hard to accept it, but that’s the reality of what happened on the pitch.”
Fifth-placed Arsenal now look set to miss out on Champions League football, with north London rivals Tottenham Hotspur needing just a point to secure fourth place.
"Incredibly disappointed,” Arteta told BBC Sport. “The way we started to the finish, Newcastle were better. They deserved to win by a mile. It's a really difficult one to accept.
"We haven't been able to deal with situations throughout the season. The squad suffered a lot with injuries, but that can't be an excuse. Newcastle were 100 times better than us.
"The way we competed today (was disappointing). In every department, you have to earn the right to play – and we didn't do it.
"We have to put our head down and accept the performance was nowhere near the standard required for the Champions League. From tomorrow, we'll prepare for Everton. It's still mathematically possible."
Newcastle head coach Eddie Howe said: “This was the best performance since my arrival. The motivation was personal pride, and performing in front of our supporters, and leaving on a good note into the summer.”