Before the game he talked the talk. By half-time Jerome Thomas had walked the walk – the walk of shame.

The red mist brought a red card for Albion’s talented new winger as his side slid out of the Carling Cup to Arsenal’s latest group of precocious kids.

And, with one stupid flick of a hand, the former Gunners prospect undid all his good work from the previous 130 promising minutes of football.

He and the Baggies will never know whether he cost them their place in the competition when he shoved Jack Wilshire in the face in a retaliatory act of petulance just before the break. But what is indisputable is the fact Thomas cost his new side the chance to push his former employers all the way.

Thomas aside, Roberto Di Matteo’s side could leave north London with their heads held high despite slipping to their first defeat in 11 League and cup matches under the new head coach.

But, having performed so well, they will have woken this morning with a lingering regret that half-an-hour of chasing the Gunners youngsters with 10 men finally took its toll as the home side struck two unanswered goals in the final 22 minutes.

Even a man down, Di Matteo’s side had moments of promise. But with a full complement the visitors had matched their talented hosts stride for stride and looked just as likely to progress to round four as Arsene Wenger’s latest class of youngsters.

It was the home side who made the running in the opening moments and a lax moment from the Baggies could have seen them behind inside three minutes.

A corner from the left by Wilshere found Philippe Senderos unmarked at the near post but he headed wide. And, when the visitors switched off again moments later from another Wilshire corner, Senderos got there again but headed over.

But Albion settled quickly and began to enjoy some decent possession and ask questions of the home defence.

And they could have led on 16 minutes when Filipe Teixeira chested a diagonal ball from Graham Dorrans into the path of Robert Koren, whose shot passed through the legs of Mikael Silvestre and a foot past the far post. There was a scare for the Baggies when Wilshire and Sanchez Watt exchanged passes following a cross by Kieran Gibbs but Dean Kiely grasped the ball before Watt could shoot.

And Albion went close three times in the moments that followed. First Luke Moore drifted wide and squared for Simon Cox, who turned Silvestre and saw his low shot saved by keeper Wojciech Szczesny.

Then Cox turned provider for Koren, whose shot on the turn was pushed wide.

And finally a terrific goalmouth scramble saw Cox’s header blocked on the line before Jonas Olsson sent a follow-up wide.

But the visitors were left facing an uphill battle seven minutes before the interval thanks to Thomas’s moment of madness.

Wilshire went down dramatically under the winger’s challenge and the duo exchanged words before Thomas inexplicably shoved a hand into the teenager’s chin and left referee Lee Mason, who was just yards from the incident, with no option but to brandish the red card.

Albion were up against it but they defended solidly at the start of the second period, waiting for a chance to arrive on the break. And it came just after the hour when Moore’s persistence wide on the right paid off and he teed up Gianni Zuiverloon.

The Dutchman’s excellent cross found Cox, who did everything right to get in front of Kerrea Gilbert, only to send his header over the bar, to his obvious anguish.

Moments later he broke clear again and fired a tame shot straight at Szczesny and that was his last act before the Baggies shored up their midfield by replacing him with Youssouf Mulumbu.

The visitors continued to impress and a powerful, jinking run by Mulumbu from inside his own half to the Arsenal byline delighted the travelling fans.

But the Gunners broke through on 68 minutes to leave Di Matteo’s men in deeper trouble.

Olsson failed to challenge substitute Carlos Vela as he broke through and Kiely could only parry the Mexican’s shot into the path of Watt, who converted clinically from close range.

Albion continued pressing but they were undone again with 15 minutes to go as Arsenal scored again through a combination of their brilliance and Leon Barnett’s embarrassing error.

The brilliance came from Aaron Ramsey’s fantastic deft through-ball and Mark Randall’s wonderful chip that beat Kiely but bounced down off the underside of the bar.

The embarrassment came when Barnett failed with the easy task of chesting back to Kiely and Vela nipped in to force the ball home from close range.

Albion should have reduced the arrears when a fine ball from Teixeira picked out substitute Chris Wood but the teenager snatched at his shot and it flew wide.

And so Di Matteo finally knows how it feels to be a losing Albion boss. But the Italian will doubtless have been less worried by the end of the Carling Cup run and more concerned about the potential knock-on effects for the Championship campaign.

With injuries mounting, Thomas’s foolishness has given the Italian an extra problem he could have done without.

And, with a blood-and-thunder Crystal Palace side looming on the horizon, a 50-minute shift with a one-man disadvantage will have done little to help preserve fresh legs in the camp.

By Steve Madeley.