The Blues suffered their second defeat in the Premier League under the former Borussia Dortmund and Paris Saint-Germain head coach.
Chelsea could have all-but secured a top four finish with a win against the Gunners, but failed to build on their recent momentum in all competitions.
The hosts started on a front foot and could have taken the lead when Kai Havertz pounced on Arsenal’s defensive mistake at the back, but the Germany international failed to execute.
Arsenal broke the deadlock on 16 minutes when they took advantage of a howler from midfielder Jorginho and that was enough to lift the visitors to eighth position on the Premier League table.
Speaking to the media after the game Tuchel admitted he was gutted with his men’s performance.
"The first half was OK, it was enough to lead 3-0 but we were 1-0 down because we forgot to score at the other end and then scored an own goal practically, I don't know how Arsenal would've scored if we didn't give it to them ourselves,” he said.
"We were not sharp enough, not the same energy as usual. We are responsible, I am responsible, we are all in this together so it was not enough to win the game.
"Bit angry that we had so many changes, that's on me, not so happy in the end with the line-up, but I didn't know what would happen, I didn't feel us like I normally do and we can't expect to win games if we're not 100% in games.
“We didn't have a shot for almost the whole second half, then we had a big one, maybe we deserved this today, we learn something.
"I'm not happy with what I saw, I have my responsibility because I picked the line-up, but the performance was the performance."