Pogatetz was sent off during Manchester United's 3 - 1 Curling Cup win for a challenge that infuriated Sir. Alex Ferguson.
Possebon was stretchered off but has not broken his leg as was first feared.
Pogatetz said: "Misjudged the challenge" and wishes Possebon "a speed recovery".
"I am going to speak to Rodrigo by telephone and I will apologise for hurting him. I hope that he'll make a quick recovery and that he won't be out for long," added Pogatetz
A statement on United's website read: "We can confirm that Rodrigo did not suffer a break to his right leg. He was kept in Hospital overnight for observation and to assess whether there was any ligament damage to his knee."
Pogatetz will miss Middlesbrough's next three matches.
Source: BBC Sports.
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