Burnley manager Owen Coyle was angry that Everton's first goal in their 2-0 win over the Clarets was allowed to stand.
James Vaughan slammed home a Marouane Fellaini cross in the 83rd minute but Yakubu appeared to be in an offside position as he missed the ball before it fell to the young striker at the back post.
Coyle argues that Yakubu was definitely offside and that his presence obstructed goalkeeper Brian Jensen, whose view was blocked as the shot came in.
"There's no doubt Yakubu's offside on the line," he told Sky Sports.
"It's a difficult one for the referee, he's looking for his assistants to help him out, that's why they're there, and he's not seen that.
"I mean the lads hit the shot and Brian Jensen, my goalkeeper, can't see the ball because Yakubu's standing right in front of him on the goal-line.
"Now I'm not suggesting for a minute that it wouldn't have gone in if Yakubu wasn't there, who knows?
"But what I do know is that Brian has not been able to see that ball.
"Yakubu was definitely offside in front of Jensen, he is a big lad and our keeper could not see the play. Jensen stuck out a foot, but Yakubu was clearly interfering with play.
"Howard Webb is a good referee and he was in no position to see it, but he should expect to get assistance from his linesman, who could surely see where the Everton player was standing when the ball went into the net.
"It influenced the game. I just want fair decisions and that was not fair."
Burnley went down to 10 men with half an hour remaining after Stephen Jordan picked up a second booking for pulling back Steven Pienaar.
Coyle thinks the defender will learn from his mistake and had no complaints with referee Webb on this occasion.
"He will learn from that, he made the referee's decision for him with already having been booked," he added.
"He will learn that in that situation you do not pull someone back, you let it go and don't get yourself booked again."