Guthrie's challenge in the final moments of the Tigers' shock 2-1 victory saw him issued with a straight red card and Fagan left the ground on crutches.

The Tigers confirmed on their official website, www.hullcityafc.premiumtv.co.uk that the damage was revealed by an X-ray this morning.

The 25-year-old former Derby striker suffered a fractured right tibia and the club state the injury is likely to keep him out of action for between six weeks and three months.

Tigers manager Phil Brown was scathing in his assessment of Guthrie's tackle.

"It cannot be tolerated, it needs to be kicked out of the game," he told the Hull Daily Mail.

"When you see that the end product is him putting a fellow pro in a cast, it's just not right.

"That's the horrible side of the game. I don't care what is going on at Newcastle, you cannot tolerate this.

"If I go back to the incident, my players were killing time in the corner, something that every Premier League club does, no matter who you are.

"In the process of doing that, someone has decided to take the matter into his own hands and lashed out at Craig Fagan."

Guthrie later expressed regret for the crunching tackle and claimed it was "totally out of character".

"I was very upset to hear the news concerning Craig," he told his club's official website, www.nufc.co.uk.

"The club have been in touch with Hull City on my behalf because I want to speak to Craig in person to apologise and wish him a speedy recovery. I hope to be able to do that as soon as possible.

"It was a challenge that came purely out of frustration towards the end of Saturday's game, but anybody who knows me will accept it was totally out of character on my part."