Mesut Ozil scored the winner as Arsenal beat Middlesbrough
Alexis Sanchez and Mesut Ozil scored either side of an Alvaro Negredo strike.
Arsenal player ratings against Middlesbrough Mon, April 17, 2017
Click through the gallery for the Arsenal player ratings against Middlesbrough
Play slideshow Getty Images 1 of 11
Petr Cech – 7: Made a crucial save when the defence failed him
The win has helped lift the pressure on manager Arsene Wenger, who was the subject of more supporter protests.
And Koscielny acknowledged the signifcance of the win at the final whistle.
"It was important to have the three points, we were in a bad situation," he told Sky Sports.
"We had to come back with quality, it was not perfect but we tried and it's good to come back with the win.
"It's good for confidence, which will come back slowly. We are intelligent, we have experience to play a different system."