It was a terrible night for the Gunners as their 2-0 defeat saw them surrender their advantage to north London rivals in the race for fourth spot.
Barring an unlikely defeat for Spurs at the Premier League's bottom side Norwich on the final day, Arsenal are set for another season playing in the Europa League.
And Xhaka didn't hold back in his verdict of his and his teammates' performance.
"It's so difficult to find the right words after the game," Xhaka told Sky Sports.
"We came here to show a different game but from the first minute until the 90 minutes we didn't deserve to be on the pitch today."
Xhaka also suggested the Arsenal players aren't doing what manager Mikel Arteta is telling them to do.
When asked why it was such a below par performance, Xhaka responded: "I don't know. I can't explain to you why.
"We didn't do what the game plan was, not listening to the coach, doing our things and when you do your things these games happen.
"What happened was a disaster performance and [playing] like this you don't deserve the Champions League, you don't even to deserve to play in the Europa League.
"It's very hard to take at the moment and I don't know why we're not doing what the coach is asking for us."
It's been suggested the pressure got to the Arsenal players with huge amounts on the line, and while Xhaka didn't subscribe to the view they suffered from stage fright, he gave a simple message to anyone who have been feeling it.
"If someone isn't ready for this game, stay at home. Simple as that," he added.
"Age doesn't matter. You can be 30, 35, you can be ten, you can be 18. If you're not ready for that, you're nervous, stay on the bench or stay at home - don't come here.
"We need people to have the balls - sorry to say that - to come here and to play because we knew this was maybe one of the most important games for us but to perform like this is not acceptable.
"Very, very sad for us, I'm very, very disappointed and I feel very sorry for the people who came here to support us. I feel very, very sorry for Arsenal supporters. This is not the way we wanted to go and I can only say sorry to them."