Arsenal may have been thoroughly impressive against Borussia Dortmund in their midweek Champions League win, but it was back to reality for the Gunners in the first-half.
Arsenal created only a couple of real chances, with Ben Foster quickly out to narrow the angle and save Danny Welbeck's shot and Aaron Ramsey going close after driving into the box. The Welshman dragged his shot wide of the post, though.
The only other time the Baggies were under any real pressure was when Foster gifted the ball to Olivier Giroud, starting a game for the first time since August, on the left but the Frenchman was at too narrow an angle to find an empty net.
Nacho Monreal, starting at left-back after the return of Laurent Koscielny, went off injured after about 20 minutes but in truth the first half was played at a very low tempo.
West Brom were content to sit back and play largely on the counter, but failed to threaten when they were in possession.
In fact, Alan Irvine's team didn't manage a single shot at third-choice Emiliano Martinez's goal.Reuse content