London - A quick-fire first-half brace by Olivier Giroud was enough to give Arsenal a comfortable 2-0 victory at home to Championship high-fliers Middlesbrough, who had eliminated Manchester City in the 4th round.
The French striker opened the scoring in the 27th minute at the Emirates Stadium, steering home a low cross from Kieran Gibbs.
Arsenal, who handed a debut to new defender Gabriel, added a second goal barely two minutes later when Giroud capitalised on inattentive marking to meet Alexis Sanchez's left-sided corner with a deft near-post volley.