Arsenal defender Mertesacker hails Koscielny performance at Man City
Mertesacker was full of praise for Thomas Vermaelen's understudy, who was making his first league start of the season.
The German told Sky Sports 1: "We had to be strong today, it was a very difficult match for us.
"We have a great squad this year and a lot of great centre-backs at the moment.
"Thomas is at home a little bit ill and Laurent came in and did fantastically. It was a solution.
"We are a strong squad and we have to stick together. We did well today and we have to keep on going."