Had relatively little to do but looked perhaps a little too loose when called into action - could have done better when parrying Dorrans’s first-half ripper, for example.
Very adept in his positioning and totally calm in keeping watch over the West Brom forwards.
Had absolutely no trouble in keeping a lid on Berahino et al, always switched on to get in the right place at the right time.
The Arsenal fans made clear their desire for the right-back to sign a new contract and he proved his value to the Gunners with a strong contribution in both attack and defence.
Untroubled by Amalfitano, the left-back was booked for a clear pull on Sessegnon but that was the only blot on a performance that was simply as good as it needed to be. Taken off for Vermaelen.
Travelled all over the pitch in a real box-to-box performance. Solid in defence but, when getting forward, his decision-making left a little to be desired.
Arsene Wenger promised more to come from the German in his programme notes and the club-record signing quietly played some delightful passes and show off some fancy footwork, a reminder of the quality that the Gunners have on their hands. Their best - almost only - threat in the second half.
Diligent and clear-headed in midfield, an unspectacular but error-free outing for the Arsenal skipper. Withdrawn for Kallstrom midway through the second half.
Delivered the fine corner from which Giroud broke the deadlock but guilty of missing a good chance on the volley later in the first half. Taken off for Rosicky after going quiet.
Got a confidence-boosting goal by comprehensively besting Craig Dawson at a corner and was a busy presence up front, working to draw the West Brom defenders out of position to some success. Booked for a pointless late confrontation with Dorrans.
Looked to get at Dawson on the Arsenal left a few times but rarely found opportunities to unleash his rocket-powered left foot. Unlucky not to score in the second half, though, his shot coming back off the post.
Put up a good fight, making several saves - although he did not face anything exceptionally testing. A little suspect in his kicking, however.
Deputising at right-back, the England Under-21s international was culpable for some very poor marking for Giroud’s goal but one wince-inducing blow proved his commitment from open play, at least.
Better at marking at corners than some of his defensive colleagues, the Uruguayan put in a reasonable performance.
Apart from one awkward but inconsequential slip, the centre-back stood relatively strong against Giroud.
Wandered around in plenty of space between the midfield and attack but West Brom rarely had the ball to send to him there and he carried little forward threat.
Suspect in his marking at set-pieces and his improvement in possession in the second half was really only prompted by Arsenal's waning pressure. A late withdrawal to make way for Vydra.
Though one of West Brom’s best players this season, the on-loan Frenchman was entirely anonymous in the first half and, though more active, stymied in the second. Withdrawn for Anichebe.
Almost entirely out of the game in the middle of the park, with the likes of Flamini dominating possession there and the Gunners focusing on attacking the flanks.
Thrust into an unfamiliar left-back role, the Baggies captain was often a target for the Arsenal attacks but held relatively firm.
Stung Szczesny’s palms with a strong long-ranged shot in the first half, one of his side’s only moments of real threat, but did little else. Booked for his part in a silly late confrontation with Giroud.
On one or two occasions, displayed some danger, with one particular cut inside and shot just over the bar the most eye-catching, but could have done more to pressure the Arsenal back line and turn the tide of possession.