VIDEO: Koscielny gaffe gifts Sunderland opening goal vs. Arsenal

What was Laurent Koscielny doing here?

Sunderland opened the scoring against Arsenal in their third-round FA Cup match at the Emirates Stadium after the French defender had a mental lapse in the 17th minute of play.

The Black Cats took an unexpected lead as Jeremain Lens robbed Koscielny of possession with his left foot, before shooting it past Petr Cech with his right.

Arsenal found an equalizer moments later, however, Joel Campbell tapping home a counter-attacking effort in the 26th minute.