The Gunners found Championship leaders Leeds more than a match for them in a goalless first half but Mikel Arteta's side came out firing in the second and were rewarded ten minutes after the restart when 20-year-old academy graduate Nelson scuffed home his second Gunners goal.
Arteta was removed from happy with Arsenal's first-half displaying, nonetheless, admitting he let his gamers realize it through the interval.
"I tried to tell them exactly what they were going to face and after 32 minutes we had won one duel".
'We changed our attitude, desire and organisation at half-time and then we were completely different'. To play against them is painful like going to the dentist - it's tough.
"What they've achieved, to do it persistently each three days with these gamers, and what they've constructed there, is highly effective".
Nevertheless, there were encouraging signs for Leeds as they gave the Premier League giants an uncomfortable evening and they will hope to do the same in a top flight fixture next term.
"Thank God, I wasn't happy at all [after the first half]".
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"I don't even think about that possibility with Auba", said Arteta.
Freeman can play as a midfielder as also as a winger and he would add significant quality and depth to the Leeds side. Leeds are a great team and they pressed us; we didn't expect it.
Arteta said: 'They are a nightmare for every team to play.
Leeds are now joint-top of the Championship, ahead of West Brom on goal difference alone but nine points clear of their next-closest competitors.
Fresh off the back of beating Manchester United in the Premier League, Arteta named a strong side for this third-round FA Cup clash as the Spaniard made only four alterations. They responded because they understood this not what we want'. We need to be united more than ever.
'Now I'm really pleased but we saw two different teams from the first to second half. "We couldn't do that in the second half".