Arsenal suffered their second defeat from their opening four Premiership games of the season after losing 2-1 at Middlesbrough.
Yakubu scored against the run of play and was then involved as Massimo Maccarone took advantage of a defensive blunder to hit the second.
Jose Antonio Reyes struck an injury-time consolation for Arsenal and also hit the post in the first half.
The Gunners had ample opportunity to take something from the game but failed to capitalise on their chances.
The result could have been so different had Arsenal made their overwhelming dominance in the first 40 minutes pay.
Within the opening 30 seconds Reyes got away from Ugo Ehiogu and produced a stinging low drive which nearly skidded underneath Mark Schwarzer's dive.
The Spaniard came even closer in the fifth minute after Dennis Bergkamp and Alexander Hleb had passed their way through the Middlesbrough defence and set up Reyes who drove against the far upright.
Reyes' third effort of the match was less distinguished, flying over the bar from 20 yards.
Robert Pires was denied by Gareth Southgate's block as Arsenal maintained the pressure, but manager Arsene Wenger must have been frustrated his players had not turned their dominance into goals.
A terrific move begun by Reyes nutmegging Xavier ended with Bergkamp producing an unexpected first-time shot from the edge of the area, but the Dutch striker could not keep the ball down.
Reyes then looked poise to strike but, when cutting back inside Ray Parlour, the ex-Gunner was wily enough to baulk his progress without conceding a penalty.
Arsenal tried again with a break the length of the field which ended with Schwarzer saving again from Reyes but after missing so many chances it was almost inevitable Middlesbrough should score with their first attempt on goal in the 40th minute.
Yakubu, who hitherto had looked rather lumbering, picked up possession from George Boateng with his back to goal. He momentarily lost control but turned to find the ball at his feet and within an instant had bent it low inside the post for his first goal for Middlesbrough.
Taking the lead gave the home side confidence, and Rochemback tried his luck with a free-kick from mind-boggling range which arrowed not too far wide.
Adam Johnson began proceedings in the second half with a storming run into the Arsenal box which was only just halted by Pascal Cygan, before Parlour blocked a Reyes' effort at the other end.
Ashley Cole was blocked out by Ehiogu after Hleb had done excellently to pick him out in the box, before Jens Lehmann pulled off a top-class reaction save to prevent Yakubu increasing Boro's lead.
That respite did not last long however after a defensive howler saw Arsenal fall 2-0 behind in the 59th minute.
Yakubu's physical presence was again a factor and though he was dispossessed by Lauren's tackle, Cygan and Kolo Toure hesitated and the ball ran through for Massimo Maccarone to slip the ball past Lehmann for a simple finish.
Wenger sent on Cesc Fabregas and Robin van Persie to try to conjure a comeback but it was Middlesbrough who seized the match by the scruff of the neck.
As the self-belief drained away from Arsenal, their touch deserted them, passes went astray and panic set in.
Yakubu would have made it a shocking 3-0 had an offside flag not intervened.
Only in injury did Arsenal reassert themselves.
Reyes, the only Arsenal player on form, hit an angled drive which Schwarzer managed to turn aside, but he was not to be denied when he swept onto a van Persie flick, rounded the keeper and scored.
Cole could have grabbed an astonishing equaliser but he stabbed wide from 18 yards.
