Arsenal boss explains surprise substitution.
Campbell had been brought into the side after two consecutive defeats, and made an instant impact by putting the Gunners 1-0 up.
With the score at 1-1 in the 63rd minute, Wenger brought Campbell off, and boos rang around the Emirates Stadium with fans dismayed to see arguably the best player in the team on the night being substituted.
Danny Welbeck came on in his place and failed to have an impact, while Arsenal went on to lose 2-1.
After the game Arsene Wenger spoke in his press conference about his thought process in bringing the Costa Rican off.
He told Arsenal.com: "Campbell hasn’t played for a while and he started to tire. He played against a very young left back and I thought Welbeck could give him some problems with his runs in behind.
"These kinds of decisions don’t mean that Campbell did badly. I think he did quite well tonight. I also think that there was room on that flank to be very dangerous."
The defeat was a costly one for Arsenal as they fell six points behind Leicester and failed to draw level on points with Spurs, who had lost to West Ham.
Campbell did make a strong chance to start the North London derby, but Wenger's decision remains to be seen.