An uninspiring Arsenal were deservedly beaten 1-0 by Sheffield United at Bramall Lane on Monday night, with poor defending costing them once again in the Premier League.

Lys Mousset got the game's only goal when he was left unmarked in the six-yard on 30 minutes as the Gunners failed to defend a corner, leaving them to rue the defensive errors that have cost them time and time again.

Unai Emery made one change from the side that beat Bournemouth before the international break, with Joe Willock replacing Dani Ceballos in midfield, while Mesut Ozil missed out on the squad once again.

In an end to end opening to the game, Arsenal had the best chance when they broke at pace with 20 minutes played.

Bukayo Saka fed a marauding Sead Kolasinac down the left, and he squared for Nicolas Pepe on the edge of the six-yard box, but the club-record signing miscued what should have been a simple finish for the opener.

Despite a relatively even opening to the game, the home side took the lead with half an hour gone as the Gunners' defensive frailties reared their ugly head once again.

A corner to the back post wasn't dealt with, as Jack O'Connell heading into the six-yard box for an unmarked Mousset to turn home and put the Blades ahead.

Arsenal thought they had won a penalty just five minutes later when Saka went down under a challenge from George Baldock, but referee Mike Dean booked the youngster for diving, despite some contact from the Sheffield United full-back.

Granit Xhaka then forced a superb save from Dean Henderson on the stroke of half-time, with the goalkeeper at full stretch to keep out his half-volley out after a neat move broke down.

The Gunners were seeing most of the ball after the break, but a lack of tempo and runners off the ball saw them repeatedly halted by the hosts, with Dani Ceballos' deflected shot the only chance of note before the hour.

United had chances of their own too, with John Fleck coming closest as his powerful drive hit the side netting.

The home side's solid defensive display forced a frustrated Arsenal into shots from range, with Pepe going close on 73 minutes as he curled an effort just wide of the post.

The Gunners couldn't find a way back, falling to their second Premier League defeat of the season in a performance that will anger most fans, with plenty of work needed if they want to make the top four this season.