Chris Wilder has revealed Sheffield United are working with police to deal with social media abuse aimed at the club's players this season.
The topic of online abuse has hit the headlines recently after referee Mike Dean was subjected to death threats after sending off Tomas Soucek in West Ham's weekend draw at Fulham – the red card was reversed after an appeal.
Speaking ahead of his side's FA Cup fifth-round tie against Bristol City at Bramall Lane, Wilder revealed the Blades have suffered their own issues this season.
Wilder called the perpetrators of online abuse "cowardly, disgusting and inhumane", and insisted that those responsible "need nailing".
"I'm not going to talk about it in detail but there's ongoing stuff at our club with the police," Wilder said. "That's as much as I'll say and I don't think the police should be dealing with it, but they've been brilliant.
"Sometimes it crosses the line and it has at our football club, hence the situation we're dealing with. There's arguments, banter and debate and people don't agree with each other, but there's a line and it's been stepped over for everyone.
"Mike Dean is an honourable referee and a decent guy, and these guys are doing their best, as the players and coaches are. They don't deserve it. It's disgusting, the individuals need nailing and I wish I could nail them in my way, but I won't be allowed to.
"We've all been subjected to the abuse and I think it's cowardly, disgusting and inhumane. We've all suffered and shouldn't have to. It isn't football and it isn't life. No one should be able to get away with it.
"There's stuff at the club that I can't discuss that players have received and it's not acceptable."
The Blades will on Wednesday night be looking to reach the quarter-finals of the FA Cup for the second year running.
United's first win of the season came in the cup at Bristol Rovers in January, sparking a good run of form which brought Premier League victories against Newcastle, Manchester United and West Brom.
Wilder admits the competition has played an important role in recent results, saying: "It was important we played a strong side at Bristol Rovers and important to back that up against Plymouth (a 2-1 fourth-round win on January 23).
"I want to win games of football and when we get deep into a competition and there is an opportunity of achieving something then we will try to do that, and that has always been the case with me during my time at Sheffield United.
"But the two games so far in the competition have definitely taken on more importance than perhaps they might have done in the past.
"What has happened in the last two or three weeks is we've got the wins we hoped we might have done earlier in the season, and that has come on the back of us winning the two FA Cup games we would have expected to win."
Lys Mousset (various niggles) and Enda Stevens (calf) could return to the squad along with Ethan Ampadu, who was ineligible against parent club Chelsea on Sunday.
George Baldock (hamstring) remains a doubt after missing out against Thomas Tuchel's side.
