Championship wrap: Derby win in style
Richard Keogh, Jeff Hendrick, Conor Sammon, Will Hughes and Jamie Ward opened up a five-goal buffer for Derby with just over 20 minutes remaining against a lacklustre Watford outfit.
Matej Vydra netted a late consolation goal for Gianfranco Zola's men as Derby secured their first win at Pride Park since running out 3-2 winners against Crystal Palace on March 24.
Nottingham Forest and Blackburn both maintained their unbeaten starts to the season on Saturday.
Forest accounted for newly-promoted Charlton Athletic 2-1 thanks to a long-range free-kick from Lewis McGugan on 17 minutes and Sam Hutchinson's strike 15 minutes from time, while Blackburn left Elland Road with a point after playing out an entertaining 3-3 draw.
Steve Kean handed a debut to Scottish international striker Jordan Rhodes but defender Markus Olsson opened the scoring against Leeds in the 19th minute before Nuno Gomes doubled their advantage eight minutes later.
Former Blackburn striker El Hadji Diouf reduced the deficit and Ross McCormack equalised in the 56th minute.
Luciano Becchio completed the sensational comeback nine minutes later however Rochina levelled proceedings in the 84th minute to ensure Blackburn preserved their unbeaten status.
Elsewhere on Saturday, Irishman Andy Keogh netted a brace as Millwall disposed of promotion hopefuls Middlesbrough 3-1 at The Den, Crystal Palace collected their first three points of the season with a hard-fought 2-1 win at home to Sheffield Wednesday and Barnsley edged Bristol City 1-0.
Birmingham condemned Peterborough to its fourth consecutive defeat of the season following their 1-0 win and increased the pressure on under-fire manager Darren Ferguson, Steve Bruce's Hull City accounted for Bolton 3-1, while Huddersfield held Ipswich to a 2-2 draw.
Craig Mackail-Smith scored twice as Brighton climbed up to fourth with a 3-1 win at struggling Burnley, while Blackpool made the trip to Leicester and suffered a 1-0 defeat - their first of the campaign.