FA cup holders Arsenal have been knocked out of the tournament at the third-round stage after they were defeated 4-2 by Championship club Nottingham Forest.

Eric Lichaj headed the hosts in front after 20 minutes but Per Mertesacker equalised shortly after for the Gunners.

Forest striker Lichaj then scored a magnificent volley at the end of the first-half to restore his side's lead.

Ben Brereton converted a penalty after 64 minutes to make it 3-1 for Forest, only for Danny Welback to pull one back for Arsenal in the 79th minute.

But Everton loanee Kieran Dowell scored from the spot shortly after to secure a memorable victory for the two-time European Cup champions.

"I knew before coming here, it would be a tricky place to go," said Wenger afterwards.

"You know when you come back it was important not to make a mistake again - that's why it's disappointing because during the game, we repeated the same mistakes and that's where we were guilty today. Once, twice, three times, and at that level, you cannot afford that.

"We were not good enough anywhere, not at the front, not in the middle, not at the back, and we paid for it. They looked sharper, had more chances, and that's all I can say. They had an outstanding performance and I couldn't fault any of their individual performances.

"Overall you can congratulate Nottingham Forest for an outstanding performance - sharp, winning decisive challenges, always dangerous going forward and overall they deserved the win today. Simple as that."