Given a lifeline by Cesc Fabregas's late equaliser from the penalty spot in north London 11 days ago, Arsenal moved through to face League One Huddersfield Town with goals from Samir Nasri, Bacary Sagna and Robin van Persie.
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It was never comfortable for Arsenal, however, as Championship Leeds were given hope by Bradley Johnson's pile-driver shortly before half-time after the Yorkshire club had fallen 2-0 behind.
Leeds could not live with Arsenal's pace and movement in the opening exchanges and Nasri stroked the visitors ahead with just five minutes on the clock to silence the vast majority of a 38,000 crowd.
When Sagna's powerful rising drive from a tight angle evaded Kasper Schmeichel after 35 minutes there looked no way back for Leeds but Johnson had other ideas, connecting sweetly from 25 metres with a stunning shot that left Wojciech Szczesny clawing at thin air.
The home side had a couple of chances to equalise in the second half but Arsenal held firm and substitute Van Persie headed the clinching goal from Nicklas Bendtner's pinpoint cross with what was virtually his first touch.
