Manchester United manager David Moyes admitted he was worried about captain Nemanja Vidic's head injury, sustained in the 1-0 win over Arsenal on Sunday.
Just before half-time Phil Jones and Arsenal goalkeeper Wojciech Szczesny clashed heads, for which Szczesny seemed to come off the worst and Jones received a booking.
Serbia defender Vidic then suffered a head injury in a similar incident a few minutes later after he collided with his own goalkeeper David de Gea's knee, and remained on the ground for a number of minutes.
When he got up he was led down the tunnel holding his head and was replaced by Tom Cleverley at the start of the second half.
Moyes said: "He's gone to hospital. I've only just seen it myself.
"I didn't see how bad it was from the touchline, but now I've had the chance to look at it again it's a terrible sort of clash, it's an accident and hopefully he'll be okay.
"I'll find out more from the medics later on."
United recorded a goalless draw in their midweek Champions League clash at Real Socieded and Moyes was delighted to get back to winning ways.
He said: "This was a big result for us today. Arsenal have been in terrific form this season and we had to play well ourselves today to get the result.
"I thought we started the game well and we were very good in the opening 20 to 30 minutes of the game. And I thought, in the end, our whole determination of effort, commitment and good play helped us in the second half when we were under more pressure."
Moyes believes the Premier League title will be a close call this season, and added: "I don't think anyone's going to run away with it.
"I think there are a lots of ups and downs, it's a close-run league this year.
"I think there will be a few shocks and we've think we've had one or two at the early part of the season, but I'm pleased we've been able to show a little bit more consistency and a bit more momentum, and let's hope we continue that."
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