An internet troll has been offered $25,000 (£16,000) to fight Brandon Marshall, wide receiver for the NFL's Chicago Bears.
A user on Instagram, AnthonyGKalla, angered Marshall after calling his mum a "w****" on the picture sharing app.
Kalla, a fan of the rival Detroit Lions, who find themselves top of the NFC North with a record of 7-2, compared to Chicago's 3-6, also said: "Remember when you called Detroit the little brother? haha.
"Well look whos [sic] at the bottom now you b****!"
Marshall, who stands at 6ft 4in and weighs more than 16 stone, initially offered $5,000 and said he'd hand over another $10,000 if he lost, saying that Kalla had to serve 100 hours helping in an orphanage if Marshall was the victor.
Kalla then responded saying: "Cmon brandy make it 25 and we can do it in Detroit".
Marshall accepted the counter-offer saying: "Ha! You thought I wouldn't say yes", before adding: "and you have to apologize to my mom".
Later on in the evening Kalla then appeared to set a date of 14 February next year, with the message: "St. Valentines day massacre homie. let do it. and to the people that want to see it im selling tix".
@AnthonyGKalla If I lose I'll give you another 10k. If I win you have to serve a 100 hours at an orphanage. Deal?— Machine Marshall (@BMarshall) November 13, 2014
Looks like people took my boxing match for charity too serious. #chill— Machine Marshall (@BMarshall) November 14, 2014
It is unclear whether Marshall intends to go ahead with the fight. The receiver later posted that people had been taking his offer "too serious", after multiple users offered to fight him.