The 26-year-old Argentinian headed back to Teesside still trying to work out how his side managed to lose 3-0 at Upton Park as two goals inside the first six minutes of the second half effectively condemned Gareth Southgate's men to defeat.

Boro host the Black Cats on Saturday as they attempt to bounce back from their third Barclays Premiership defeat in six outings so far this season, and Arca will have no qualms about making his former employers pay for his disappointment.

He said: "We created lots of chances but in this league no-one feels sorry for you if you don't score and then you concede.

"But in football things like that happen and hopefully next week we can win."

Boro headed south with high hopes but after passing up a series of chances of their own - Jeremie Aliadiere and Tuncay Sanli both hit the woodwork - were undone as the second half got under way.

Lee Bowyer's 46th-minute strike was followed by a Luke Young own goal within five minutes, and although the visitors rallied once again, Dean Ashton marked his return from injury with his first goal in 16 months to wrap up the points.

Arca insisted the Hammers were flattered by the scoreline, but admitted the game was as good as over when Young turned the ball into his own net.

He said: "No-one expected us to be beaten as badly as we were. People who did not see the game will maybe think they battered us, but it wasn't like that.

"They had three chances to score and maybe one more. They were more awake than us at the beginning of the second half, and that was the point that changed the game.

"They scored two goals straight away and that changed the game. We went forward looking for a goal and they scored again, and after that, the game was over.

"We tried to keep going and tried to score a goal to change the game. In the last 20 minutes, we did okay, but the game was over."

To make matters worse for Boro, Aliadiere limped off with a suspected hamstring injury after just 30 minutes to be replaced by Tuncay.

Club medics were today assessing the extent of the damage as Southgate kept his fingers crossed that he will not be without his £2.5million summer acquisition for too long.