Martin Keown has singled out Per Mertesacker for poor defending after Arsenal were shockingly defeated in the FA Cup by Nottingham Forest.

Forest were 2-1 ahead at half-time through a brace from American Eric Lichaj before Ben Brereton and Kieran Dowell converted penalties and the game at the City Ground finished 4-2.

"Mertesacker, the senior player, you cannot leave someone that close to the goal unmarked.

"It's criminal, Lichaj has just cashed in. It's really quite poor from Arsenal there."