Merseyside Police are investigating allegations that a newspaper article about Everton midfielder Ross Barkley constitutes a "racial hate crime".
Barkley, 23, was punched in a Liverpool bar last weekend in what his lawyer described as an "unprovoked attack".
In an article on Friday, Sun columnist Kelvin MacKenzie compared Barkley - who has a grandfather born in Nigeria - to a "gorilla at the zoo".
Police confirmed they were investigating the "full circumstances".
MacKenzie targeted both England international Barkley and the city of Liverpool in the article - which has since been taken off The Sun website - saying:
- Barkley is "one of our dimmest footballers", also calling him "thick".
- His eyes make him "certain not only are the lights not on, there is definitely nobody at home", adding: "I get a similar feeling when seeing a gorilla at the zoo."
- Men with similar "pay packets" in Liverpool are "drug dealers" and in prison.
Liverpool Mayor Joe Anderson told BBC Sport he reported the article to the police for a "racial slur".
Speaking to BBC Sport, Anderson said: "Not only is it racist in a sense that he is of mixed-race descent, equally it's a racial stereotype of Liverpool. It is racist and prehistoric."
Anderson later tweeted to say he had reported the article to Merseyside Police and the Independent Press Standards Organisation.
Alongside the article, The Sun published adjoining pictures of Barkley and a gorilla on their website with the caption "Could Everton's Ross Barkley represent the missing link between man and beast?" The picture was later removed.
MacKenzie was editor of The Sun when it published a front-page article headlined 'Hillsborough: The Truth' in the aftermath of the 1989 disaster at Sheffield Wednesday's football stadium.
The article claimed Liverpool fans were to blame for the tragedy, in which 96 people died. MacKenzie apologised in 2012.
Last year's landmark Hillsborough inquests recorded that the 96 fans were unlawfully killed and that Liverpool supporters at the FA Cup semi-final had played no role in causing the tragedy.
This Saturday, 15 April, marks the 28th anniversary of the disaster.
Burnley midfielder Joey Barton, who was an Everton youth player, tweeted: "Those comments about Ross Barkley, a young working-class lad, are disgusting. Then add in the fact he is mixed race! It becomes outrageous."
Former Liverpool striker Stan Collymore tweeted: "Implied racism at its finest."
A Sun spokesperson said: "Columnists are supposed to have strong opinions that provoke debate among the readers. However their views do not necessarily reflect those of the newspaper."
Football's equality and inclusion organisation Kick It Out said they had received complaints about the "insulting and offensive" comments.
"We will be contacting Everton and the PFA about their responses in providing support to Ross and his family," they said.
BBC Sport has contacted Everton and Barkley's representatives for comment.