The Gunners lost three players to injury during a frustrating evening at the Stadium of Light with few real chances to put their names on the scoresheet as a tough week continued
The Gunners lost Francis Coquelin to injury within 10 minutes before Richardson put an end to a frustrating half with a left-footed shot that deflected off the youngster's replacement, Sebastien Squillaci, into the net.
Alex Oxlade-Chamberlain was then unfortunate late in the second half to divert Craig Gardner's cutback into his own net and confirm his side's exit.
Sunderland made only one change, Sebastian Larsson coming in for Fraizer Campbell on the right of midfield, while Arsene Wenger made five alterations from Arsenal’s 4-0 midweek mauling by AC Milan. Theo Walcott was dropped with Gervinho and Oxlade-Chamberlain occupying the flanks, while Lukas Fabianski, Johan Djourou and Coquelin were all also introduced.
The Gunners made a confident start, dominating the opening minutes and seeing Mikel Arteta’s free kick only slightly wide, but suffered more injury woes just a moment later when Coquelin was forced off inside nine minutes due to an apparent hamstring problem.
The home side needed until the 14th minute to even approach the Arsenal goal, Stephane Sessegnon picking up the ball from a quick free kick and attempting an effort from some way out, but it flew comfortably enough past Fabianski’s post.
Sunderland were growing into the game but the first real save came towards the half-hour mark when Gervinho was supplied the ball by Robin van Persie deep in the Sunderland half on the counter. Running slightly away from goal to try to escape the attentions of the covering defender, the Ivorian aimed a shot towards the top corner but Simon Mignolet parried it solidly away.
Arsenal fans shouted for a penalty when Gervinho then combined with Van Persie the other way round, bringing down a lofted pass from Oxlade-Chamberlain then almost piercing the Sunderland centre-backs clean through the middle. The Dutchman, though, was closed down just quickly enough and did not appeal when he went down.
The Gunners were controlling the game for several minutes when, towards the end of the half, Djourou gave away a silly foul near Sunderland’s right wing.
Larsson stepped up to whip in an inswinging delivery that was headed away in the area, but Richardson was on hand to pick up the rebound and aimed a riposte across the face of the goal, deflecting into the far corner off substitute Squllaci with his left foot.
Buoyed, the hosts nearly instantly doubled their lead, breaking with verve. Larsson advanced down the right and launched a long pass towards the far post where Jack Colback kept it in and teed up McClean who fired into the side netting in a crowded area.
Having controlled the game in spells, Arsenal found themselves needing to dig out of a hole as half-time arrived.
The Gunners were delivered another warning just after half-time when Sunderland got a free kick just past the left edge of the area, which Larsson dipped menacingly just over the bar.
As Wenger looked to effect changes, Ramsey succumbed to his earlier knock within a few minutes of the restart and made way for Tomas Rosicky, while Squillaci, too, had to be substituted himself with an injury as Arsenal introduced Walcott in their final throw of the dice.
The Gunners were lucky not to lose another man when Djourou slid into an awkward tackle just in front of his box with both feet. Already on a yellow, the Swiss’ challenge went ignored by referee Howard Webb.
With more than one foul starting to creep into the game, Larsson gave away a set-piece in a promising position for Arsenal, but Van Persie’s resulting shot was deflected wide by one of many bodies in the area.
As Sunderland fans started taunting Wenger and Arsenal, the game became quiet with no clear-cut chances and few moments of skill, the Gunners manager visibly unimpressed by his side's display.
Arsenal finally brought a moment of threat on 75 minutes when a free kick found Vermaelen forward in the area. The Belgian centre-back met it with a header but his effort lacked venom and was unworriedly caught by Mignolet.
The visitors pushed forward once more but Sunderland hit them on the counter, Sessegnon breezing past a slipping Arteta and advancing menacingly. The Benin international passed right to Larsson in the area, who was crowded out but still connected with the post. In reaching the goal line to help defend, however, Oxlade-Chamberlain was unluckily hit as it rebounded and could not prevent the ball bobbling over the line to deepen Arsenal's malaise.
Van Persie had a half-chance as the away side looked to revive themselves but he could only muster an effort over the bar from an unbalanced position, whilst Sunderland responded a moment later with a threatening counter, McClean hovering dangerously before Bacary Sagna cleared.
Sunderland defended resolutely in stoppage time to prevent any glimpse of genuine opportunity for Arsenal before the final whistle confirmed their progression.