The 1-1 draw hurts United title chances.
Ben Arfa said: "What's certain is I received a big blow to my head. I don't know if Rio Ferdinand got the ball but the main thing is we got the goal.
"I think if we gain in confidence, we can go and get the title.
"I think the only thing that makes a difference is the confidence. We really have good footballers here. If we carry on like this, then we can do something."