Arsene Wenger felt Arsenal were "incredibly unlucky" to fall to a 2-1 Premier League loss at West Brom as the visitors surrendered a one-goal lead and missed a penalty.
Olivier Giroud handed Arsenal the advantage at The Hawthorns, but James Morrison's effort and a Mikel Arteta own goal put the hosts in the ascendancy before the interval.
Santi Cazorla fluffed his lines badly with a late penalty as Wenger's side lost in the league for just the third time this season.
"It was a very bad day for us. We were incredibly unlucky and never deserved to lose," Wenger told Sky Sports. "We gave everything to win and did not deserve this.
"The only part where maybe we lost focus a bit was between the 35th minute and the 45th minute. Our focus was not 100 per cent then. We were lacking concentration during the set-piece for 1-1.
"We knew what to expect, but we were defensively not at our usual level and we were unfortunate in attack, because we missed a lot of chances. Then we failed to score that penalty as well.
"We are obviously very disappointed, but we cannot change what happened and we must bounce back as soon as possible."
The Frenchman also confirmed that Arteta suffered a muscular problem and Francis Coquelin picked up a knee injury, with the length of their potential absences yet to be confirmed.