What is more, manager Neil Warnock is encouraging United fans to "shop" their heroes if they see them flouting the ban.
It follows a disturbance in a public house the day after United won the Sheffield derby the previous weekend in the wake of which United's former Wednesday midfielder Alan Quinn was arrested.
Warnock said that Quinn, who is currently out of the side through injury, will be cleared of any wrongdoing and therefore escape disciplinary action. But he is so determined that nothing will undermine United's Premiership ambitions Warnock will not allow his players into a pub even for a soft drink.
"I've spoken to a number of people about the incident and Alan is in the clear as far as I am concerned, even though going into a Wednesday pub was not the brightest thing to do the day after the derby," Warnock said. "But none of my players will be going into a pub between now and the end of the season because you can get into trouble even if you are only drinking orange juice.
"We cannot let anything detract from what we want to do," he added, "and I'll tell the fans in my programme notes for the game against Crewe next Friday that if they see one of my players in a pub I'd love them to let me know."
Meanwhile, Warnock will tell his players that the Crewe game is their opportunity to right the wrongs committed on the field on Saturday, when United recovered from the loss of an early goal to lead 2-1 at half-time but then missed a penalty before allowing managerless Queen's Park Rangers to record their first away win of 2006.
The result loosens his side's grip on second place to the extent that Watford are now within seven points of catching them. Leeds, due at Bramall Lane in April, are a further point adrift with a game in hand.
"After we missed the penalty a few heads went down and we are not used to that," Warnock said. "It is now about how we bounce back."
Marc Nygaard had put Rangers ahead but Ade Akinbiyi equalised before a Marc Bircham own goal gave United the lead. Had Paul Ifill's spot-kick early in the second half not been saved by Paul Jones, United might have taken a stranglehold. Instead, Chris Morgan put through his own net to bring Rangers level and the 37-year-old Paul Furlong ran on to the excellent Lee Cook's pass to clinch victory.
"We deserved the result although the penalty was a turning point," QPR's stand-in manager, Gary Waddock, said.
Goals: Nygaard (6) 0-1; Akinbiyi (21) 1-1; Bircham og (29) 2-1; Morgan og (56) 2-2; Furlong (74) 2-3.
Sheffield United (4-4-2): Kenny; Kozluk, Morgan, Collins, Armstrong; Ifill, Montgomery (Unsworth, 63), Jagielka, Tonge; Akinbiyi (Shipperley, 78), Horsfield (Webber, 66). Substitutes not used: Flitcroft, Kabba.
Queen's Park Rangers (4-4-2): Jones; Bignot, Shittu, Evatt, Rose; Langley, Lomas (Santos, 89), Bircham, Cook; Furlong, Nygaard (Youssouf, 72). Substitutes not used: Bailey, Baidoo, Thomas.
Referee: K Friend (Leicestershire).
Booked: Sheffield United Tonge; QPR Nygaard, Langley, Shittu, Lomas.
Man of the match: Cook.