Southampton returned to the top of the Championship in emphatic style with an easy win over Derby at St Mary's.
Defender Jos Hooiveld steered in from close range from a corner to give Saints the half-time lead.
Aaron Martin then found the net from inside the six-yard box before Adam Lallana finished a superb flowing move.
Japanese striker Tadanari Lee fired in from 18 yards to score his first goal for Saints who move two points clear of West Ham, having played two more games.
With the Hammers not in action because of Blackpool's participation in the FA Cup, Southampton seized their chance to regain pole position.
Saints made two changes to their side, with Dan Harding and Richard Chaplow replacing the injured Frazer Richardson and Guly do Prado, who missed out because of illness. John Brayford and James Bailey came back into Derby's line-up as Craig Bryson and Callum Ball made way.
Saints showed plenty of attacking intent in the early stages, with Harding's free-kick from the right wing forcing Derby goalkeeper Frank Fielding to make a smart save.
Hooiveld put Nigel Adkins' men in front when the former Celtic defender bundled in Dan Fox's corner from the left.
They wasted several chances to extend their lead prior to the second goal which came 12 minutes after half-time. This time Martin was on hand to finish from close range from another corner.
Lallana drew a superb reflex save from Fielding, but the goalkeeper was unable to deny him adding a third when Fox completed a hat-trick of assists.
Lee then rifled in a magnificent effort from the edge of the box.
Victory for the Saints extended their unbeaten run in the league to five games, while, in contrast, Derby are now without a victory in six league and cup games.