Manchester United striker Wayne Rooney told a Twitter follower "I'll put u asleep within 10 seconds" after being provoked on the social networking site.
Rooney, who is new to Twitter but already has more than half a million followers, was abused by the Twitter account sam_oldham_LFC on Tuesday night, who called the England striker a "fat whore" and threatened to "smash ya head in with a pitchin wedge."
Rooney responded by inviting the Liverpool fan to Manchester United's training ground, writing: "you know where I train every day kid come and do it good luck."
After another reply from the fan, Rooney replied: "cool bring ur sandwedge girl"
Rooney then tweeted "I'll put u asleep within 10 seconds u little girl. Don't say stuff and not follow up on it. I'll be waiting".
Unfortunately, the striker made the common error of addressing that tweet to himself, but then expanded on his message and addressed it to intended recipient, saying: "I will put u asleep within 10 seconds hope u turn up if u don't gonna tell everyone ur scared u little nit. I'll be waiting."
Later, Rooney attempted to play down the situation, posting the message: "Ha ha bit of banter and people go nuts chill all people."
The account sam_oldham_LFC has now been deleted. Rooney's spokesman said: "As is made clear in the tweets, this whole exchange is banter. There is no suggestion, nor is there any intention of a suggestion, of a real fight."
Twitter has been hailed as a positive innovation which allows fans to interact directly with players, but abusive messages appear to be on the increase.
Earlier this season West Ham defender Danny Gabbidon was fined £6,000 by the English FA for improper conduct after quitting the site with the message: "U know what, f*** the lot of you, u will never get another tweet from me again, you just don't get it do you. Bye bye."
Former Liverpool winger Ryan Babel was also fined £10,000 for improper conduct in January, after posting a picture of Howard Webb in a Manchester United shirt following Liverpool's 1-0 defeat at Old Trafford in the FA Cup.