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When Greg Halford was substituted for Jamie Ward just before the halfway mark, he rejected to shake Blackwell's hand and walked straight down the tunnel. The Gaffer has explained to the on loan Black Cat his reasons in making the substitution.
He said: "We wanted to put more pressure on Cardiff, pin them in by putting another forward on. We were very mindful that Greg had picked up a booking and when I explained the situation to him afterwards he accepted it and apologised for banging the dugout - he understands.
"Why should I be bothered about his reaction? I want passion from the players."
Just in case you didn't know, Halford will be suspended for United's encounter with Ipswich after the international break due him receiving his 5th caution of the campaign.