While the centre back was delighted to play such a key role at The Hawthorns, he says all that matters was picking up the three points.
"If I score with my left foot, right foot or with my head, the most important thing is that it's a goal and it was for the team," Koscielny told arsenal.com.
"This goal was important and I am very happy for the fans, the team and the boss because we have all worked hard to be here today.
"It was very important to win because we want to play in the Champions League next year. We did the job on the pitch. Maybe it wasn't our best game of the season but the most important thing was to get the three points."