The Deputy Prime Minister, who is a Sheffield MP, said footballers were role models to youngsters and that should “weigh heavily” on the club’s owners.
Almost 150,000 people have signed a petition urging the Blades not to welcome him back but many United fans are convinced the club will allow the player to return.
Team manager Nigel Clough said the decision about whether the Welsh international striker returns to Bramall Lane will be taken by the owners.
Evans, 25, is due to be released this week after serving half of a five-year sentence imposed in April 2012 for raping a teenager in a hotel room.
Mr Clegg told LBC Radio: “I think the owners need to think really long and hard about the fact that when you take a footballer on, you are not taking just a footballer these days, you are also taking on a role model.
“You are taking on a role model, particularly for a lot of young boys who look up to their heroes on a football pitch in a team like that, and he has committed a very serious crime.”
He added: “It is for the football club to decide, but I really do think that footballers these days, they are major public figures who have a public responsibility to set an example for other people.
“I’m sure that will weigh heavily in the decisions made by the owners of Sheffield United.”
Sheffield Hallam MP Mr Clegg said it was not for politicians to tell the club’s owners what to do, but they could not “wish away” the conviction.
He said: “Rape is an incredibly serious offence, an unbelievably serious offence. He has done his time but I just don’t believe that the owners of a football club can somehow wish away the fact that that has happened.
“That is what he will be known for and that is something which, particularly for the youngsters following that team, they will always be aware of.
“I don’t think it’s right for politicians to tell football clubs what they will do and who they employ. All I’m saying is I think football players these days, they get paid a lot of money, they are public figures and you can’t ignore that.”
Evans was jailed for raping a 19-year-old woman in a hotel room in North Wales.
The footballer denied the offence but was found guilty by a jury at Caernarfon Crown Court.
He admitted having sex with her but the woman told the jury she had no memory of the incident.
The prosecution said the woman, who cannot be named for legal reasons, was too drunk to consent to sexual intercourse.
Port Vale defender Clayton McDonald also admitted having sex with the victim but was found not guilty of the same charge.
An appeal against Evans’s conviction was rejected by three judges at the Court of Appeal in 2012.
His girlfriend, Natasha Massey, has led a campaign to have the conviction overturned.
Evans scored 48 goals in 113 games for the Blades before his imprisonment, including 35 in 42 games during the 2011/12 campaign which was cut short for him due to his trial and conviction.
He has been capped 13 times for his country.