Referee Paul Tierney has a massive job on his hands when Liverpool face Manchester United. The official has been a massive talking point in the build-up to the top-of-the-table Premier League clash, not least because of Jurgen Klopp's recent comments about the number of penalties United receive.Tierney will be well aware that the fixture between these two eternal rivals has a history of turning nasty. From Javier Mascherano losing his head to Paul Scholes trying to take off Xabi Alonso's, there have been numerous red cards down the years. One man who was lucky to avoid one, though, was Jamie Carragher when he put in a heavy tackle on Nani. The centre-back was moved over to right-back mid-game and Sir Alex Ferguson immediately reacted by moving the rapid winger over to terrorise the England international. It clearly worked, as Carragher completely mistimed one of his challenges and sent Nani flying into the air. So don't get us wrong, it was a poor tackle. However, the Portuguese's reaction infuriated Liverpool players and fans' alike. Nani was known for having a fairly low pain threshold during his time at Old Trafford, but his playacting as he tried to get Carragher punished went a little too far - in fact, Wayne Rooney even claimed he started crying. 

Skip to 1:45 to see the full incident: 

On Sky Sports Football, Carragher later recalled the incident in a chat with Gary Neville. 

"Not one of my finer moments, a bit of a dive from Nani," he said. "I tell you what my best memory of that is. Not so much the tackle, but Wayne Rooney's reaction....I said 'he just beat me with skill'...and Wayne Rooney came over and said 'you won't believe it he's crying!'"

Steven Gerrard was particularly angry at Nani's over-acting and confronted him. As Phil Dowd tried to cool the situation down, the midfielder placed a hand on Nani - only for him to dive theatrically onto the floor again. 

Gerrard could be seen screaming "get up!" 

To be fair to the United man, he did appear to be genuinely alarmed at the tackle. He later said he was "lucky to be still playing this season" and refused to accept Carragher's apology. 

On Sunday, the two sides won't be fired up by the Anfield crowd but there is still every chance things could get heated with so much on the line as Ole Gunnar Solskjaer's men try to further their advantage at the summit.