This time there was no point berating a fourth official. Seven days earlier, Arsène Wenger had taken out his frustrations on the man with the electronic board after Arsenal had dropped points at the Stadium of Light, but on Saturday the Arsenal manager had no-one to blame but his players – and himself.
His own error is seen by many as failing to replace Manuel Almunia in the summer with a more reliable goalkeeper. On Saturday, the Spaniard's blunder in letting a shot by Gonzalo Jara, Albion's Chile defender, squirm past him was the key moment of the match. It gave the visitors a 2-0 lead and a valuable shot of self-belief, while the keeper's own confidence was so badly damaged that he failed to leave his line quickly enough before Jerome Thomas scored the third.
Wenger, predictably, pointed out that Almunia had also saved (and conceded) a penalty in the first half – "It was 0-0 at half-time because of Almunia..." - but by pursuing Mark Schwarzer of Fulham over the summer he had already tacitly admitted the need for a change between the posts. Now, though, he is stuck with what he has until the transfer window opens in January – which makes it all the more urgent that the team in front of Almunia quickly regains the rhythm that deserted it so completely on Saturday.
Wenger would not offer the absence of the injured Cesc Fabregas as an obvious excuse. "It has happened before, but we have still had good performances," he said. "From the back to forwards, we were flat and poor. What is most frustrating was there was no electricity. We had lost the generator. There will be some changes [for tomorrow evening's Champions League match away to Partizan Belgrade], that is for sure."
However, his options all look somewhat lightweight. Last week Wenger had defended his decision not to spend heavily on squad strengthening on the grounds that his young players would be held back, but Thomas, an FA Youth Cup winner with Arsenal in 2000 and 2001, recalled that things were different when he left for Charlton Athletic in 2004.
"In front of me in the first team were Pires, Ljungberg, Vieira, Bergkamp, Henry," he said. "As you see, now the standard – no disrespect to the Arsenal team – is not as high. That is why a lot of the youngsters are getting their chance. "
Thomas now looks at home in a West Bromwich Albion side that appears more capable than some of its predecessors of staying in the top flight beyond the usual single season. He tormented Bacary Sagna, most notably when beating him to set up Albion's first goal for Peter Odemwingie, who is proving one of the signings of the summer.
The Uzbek-born Nigeria striker experienced racism at his previous club, Lokomotiv Moscow, where his own "supporters" made a banner thanking Albion for taking him off their hands, and bearing the image of a banana. The Albion fans responded with a banner of their own, thanking Lokomotiv.
"The Lokomotiv banner made me feel a little bit bad," he said. "It wasn't a big deal, the little effort they put into it – but it was good to give the West Brom fans a result back for their support.
"I said that we should be aiming higher than just staying up and now that makes sense. I joked in the dressing room that with results like this we should be going for the Champions League. It's a big task but with football you just have to believe."
Arsenal 4-2-3-1: Almunia; Sagna, Koscielny (Vela, 66), Squillaci, Clichy; Song, Diaby (Rosicky, 56); Eboué (Wilshere, 56), Nasri, Arshavin; Chamakh. Substitutes not used: Fabianski (gk), Denilson, Djourou, Emmanuel-Thomas.
Booked: Almunia, Koscielny, Rosicky, Chamakh.
West Bromwich Albion 4-1-4-1: Carson; Jara, Ibanez, Olsson, Shorey; Mulumbu; Brunt, Morrison (Dorrans, 78), Scharner (Reid, 71), Thomas (Tchoyi, 83); Odemwingie. Substitutes not used: Myhill (gk), Zuiverloon, Fortune, Cox.
Booked Olsson, Scharner, Jara.
Man of the match Thomas
Possession Arsenal 48% West Brom 52%
Shots on target Arsenal 12 West Brom 6
Referee M Oliver (Northumberland) Attendance 60,025 Match rating 8/10.
Arsenal's options in goal
Manuel Almunia Saturday's display followed mistakes against Birmingham and Tottenham earlier this year.
Lukasz Fabianski Conceded a soft Robbie Keane shot at White Hart Lane last week after glaring errors at Porto, Stoke and Wigan last season.
Vito Mannone Has only played six games but was badly at fault against Birmingham and West Ham last year.
And Wenger's other options are...
Wojciech Szczesny impressed on loan at Brentford last season while James Shea trained with England last month.