Prop Ben Flower has received death threats after punching a defenceless Lance Hohaia in Sunday's Super League grand final between St Helens and Wigan.
Flower was yesterday handed a six month ban for his actions which saw him sent off just two minutes into his side's defeat.
A series of abusive Twitter remarks were posted on an account on Tuesday, directed to Flower, the BBC reports.
Other Twitter messages said that Flower "deserves to be shot", adding that he is a "dead man".
Greater Manchester Police (GMP) tweeted: "We've been made aware of abusive social media activity about the Rugby League Grand Final. Please be reassured that we are looking into this.