Cardiff City capitalised on Ipswich Town's slip-up to go three points clear atop the Championship, while Norwich City shipped four goals for the second time in as many league matches.
Sunderland also has plenty of thinking to do after a heavy defeat at Barnsley saw Simon Grayson's side slip to 19th ahead of the international break.
However, the news was better for Leeds United and Sheffield United as they secured second straight league victories on Sunday (AEST).
Cardiff rebounded from a midweek EFL Cup loss to Burton Albion by edging Queens Park Rangers 2-1.
Junior Hoilett and Sol Bamba combined to overturn Matt Smith's 15th-minute opener and extend the Bluebirds' perfect start.
Warnock's side is the Championship's only 100 per cent team from five matches after Ipswich Town's 2-0 home defeat against Fulham.
Neeskens Kebano and Rui Fonte netted either side of half-time to end the host's perfect start and secure a breakthrough victory for Slavisa Jokanovic's outfit.
Norwich leaked four goals for the second time in as many Championship matches as Millwall snared its first win in style.
Lee Gregory, George Saville and Jed Wallace fired the hosts to a three-goal lead at half-time before Shaun Hutchinson completed the 4-0 rout with a late header.
Barnsley recorded the day's other big win as it brushed aside Sunderland 3-0, the goals coming from Chelsea loanee Ike Ugbo, teenager Harvey Barnes and midfielder George Moncur.
The victory sees Barnsley climb a point above the Black Cats, who are now without a win in three league games.
Leeds leapfrogged Nottingham Forest into third with a 2-0 win at The City Ground while Reading prevailed by the same margin at Birmingham City.
Ezgjan Alioski's late screamer put the seal on the Whites' third away triumph of the campaign after Kemar Roofe earlier headed the visitors into the lead.
Billy Sharp's brace bookended Sheffield United's 3-1 defeat of Derby County for Chris Wilder's side, which is fifth.
The striker scored twice either side of Johnny Russell's own goal, the second coming with Scott Carson up the field attempting to turn Craig Bryson's stoppage-time strike into more than just a consolation.
The Blades are a point off fourth-placed Wolverhampton Wanderers, which drew 0-0 at winless Brentford.
Middlesbrough and Preston North End played out a goalless stalemate at the Riverside. Elsewhere, Joe Mason made an immediate impact off the bench to give Burton Albion a 1-1 draw with Sheffield Wednesday.