A year after being labelled the "Invincibles", Arsenal lie nine points behind the leaders Chelsea and level on points with promoted Wigan. The early-season defeat to Chelsea, Patrick Vieira's summer departure to Juventus and the uncertainty over Thierry Henry's future at the club have added a rare sense of vulnerability to Wenger's team.
They could have won this game at a canter, but missed chances and lost heads allowed Middlesbrough to end a run of eight straight defeats against Arsenal, leaving Wenger furious at his team's inept performance.
"We made it difficult for ourselves by missing too many chances," he said. "We lacked concentration and once they scored, they put nine men behind the ball and waited for us to make another mistake. That happened and they scored again.
"There is no reason for the players to lack confidence, but we need to find more stability at the back. Leaving here with zero points is not acceptable."
Robert Pires and Jose Antonio Reyes had clear chances to open the scoring inside the opening 10 minutes as the visitors attempted to overwhelm Boro in the early stages.
A defensive mistake by Ugo Ehiogu in the second minute gifted Reyes the ball on the edge of the penalty area and he was only denied his first goal of the season when Mark Schwarzer dived low to save his right-foot strike. Two minutes later, Reyes again went close when he waltzed through the six-yard box before hitting the far post, this time with a left-foot shot.
Boro, giving debuts to Abel Xavier, Fabio Rochemback and the 18-year-old midfielder Adam Johnson, were clearly set out to stifle Arsenal and snatch a goal on the break through lone forward Yakubu and it arrived when George Boateng was allowed the time and space to feed Yakubu just inside the Arsenal penalty area. The Nigerian used his considerable muscle to hold off Kolo Touré before beating Jens Lehmann with a mis-kicked right-foot strike into the far corner.
The goal was harsh on Arsenal and their frustrations carried over into the second half. Alexsandr Hleb fell to the ground looking for a penalty after brushing past Xavier, but the referee, Mike Riley, waved play on andBoro scored from the counter-attack.
"As soon as Hleb went down, I looked at the TV replay and it was a half dive in my opinion," said McClaren "The referee did well and we broke away and scored the second goal."
Yakubu picked out the unmarked Maccarone and the Italian, only back at the Riverside after failing to turn loan moves to Parma and Siena into full transfers, struck his first Boro goal since May 2004 to double his team's lead and add to Arsenal's sense of concern.
Despite having half an hour to rescue the game, Arsenal rarely looked like generating any forward momentum regardless of Reyes's injury-time goal. The game had already gone and perhaps the title has gone with it.
"It's about time we beat Arsenal," said the Boro manager. "It was eight straight defeats before this one and each of those games was an opportunity to end the run, but I really fancied us before this one."
With the gulf opening up between Arsenal and Chelsea, Wenger admitted that the champions are not even on his radar.
"Chelsea are not my worry," he said. "Results are my worry at the moment."Reuse content