Ryan Babel has apologised for comments he made about Rotherham referee Howard Webb in the aftermath of Liverpool's FA Cup exit to Manchester United.
The Holland international used his Twitter account to post a mocked-up picture of the Yorkshire-born official wearing a United shirt, after the World Cup referee awarded the home side a first-minute penalty and sent off Liverpool captain Steven Gerrard.
The FA confirmed last night that they would be looking into the matter, as Babel also wrote: "And they call him one of the best referees? That's a joke. SMH."
SMH is an abbreviation for "shaking my head" but the 24-year-old has since added: "My apology if they take my posted pic seriously. This is just an emotional reaction after losing an important game.
"Sorry Howard Webb."
Last January, Babel criticised former Reds manager Rafael Benitez on the social networking site, and he is not the first Liverpool player to court online controversy this weekend.
On Saturday, defender Glen Johnson, who missed yesterday's game as his wife had gone into labour, launched an attack on TV pundit Paul Merson after he criticised his performances for the Reds.
But after complaints were received about some of Johnson's comments, they were quickly deleted.
New Liverpool manager Kenny Dalglish was left to muse on how football has changed after a "joke" penalty and the sending-off of his captain condemned the Reds to a 1-0 defeat at Old Trafford.
"The penalty is a joke," said Dalglish. "I have seen the replay and unless they have changed the rules it is no penalty. The other one, I cannot see that as a red card either. In the dressing room before the game someone said to me the game's not changed that much."
Dalglish has more important matters to occupy his mind though, leaving Sir Alex Ferguson to outline a differing view of Daniel Agger's challenge on Dimitar Berbatov inside the opening 30 seconds and Steven Gerrard's subsequent lunge on Michael Carrick.
"It was a penalty," he argued.
"Dimitar says he was definitely clipped. The replay shows he slightly touched him but the momentum is enough to bring the player down."
Manchester United's reward for beating Liverpool is a fourth-round clash at League One side Southampton. The Saints, who beat Blackpool 2-0, will face Sir Alex Ferguson's men at St Mary's on the weekend of January 29-30.
There could be as many as five all top-flight ties, with Bolton at home to Wigan, Fulham up against Spurs and Aston Villa taking on Blackburn.
Chelsea will travel to Everton, while the winners of the replays between Doncaster and Wolves and Stoke and Cardiff will also meet. League Two side Stevenage, who caused the shock of the round by beating Newcastle 3-1, will welcome Reading, while Birmingham take on Coventry.
West Ham will be at home to Nottingham Forest and Watford play Brighton.
Manchester City or Leicester will head to Notts County, surprise winners at Sunderland, while Swansea will play Leyton Orient and Burton Albion will travel to Burnley.
The winner of tonight's game between Crawley and Derby will head to Torquay.