A first senior hat-trick for Emile Heskey was counterbalanced by a head injury to Michael Owen as Liverpool elevated themselves to fourth place in the table yesterday at the expense of an exceptionally poor Derby team.

Owen was taken to hospital with six stitches in the back of his head, and possible mild concussion. "The boy is strong," Gerard Houllier said afterwards, refuting the suggestion that this had been the last straw in a fairly catastrophic week for Owen.

Owen was injured in the instant that Heskey scored the first of his goals from Gary McAllister's corner on 17 minutes. As Heskey slipped in front of Rory Delap at the near post, Owen fell in the goalmouth melee and was raising his eyes to watch his fellow striker's glancing header hit the net when Chris Riggott's knee smashed into the back of his skull.

Owen's misfortune apart, Heskey was virtually irresistible while Robbie Fowler, who has started only one Premiership match in 13 months, took Owen's place and made the most of his extended opportunity. His instant through-ball eight minutes after half-time allowed Heskey to smash a spectacular right-foot shot past Mart Poom from just outside the penalty area, and his intuitive flick to Nick Barmby after 66 minutes inspired the low cross from which Heskey bundled the ball home to complete his scoring.

Barmby was also involved in the fourth goal, dummying Danny Murphy's pass 10 minutes from the end to give Patrik Berger the opportunity to score with a characteristically splendiferous left-foot drive from 20 yards. But almost the entire Liverpool team deserves the credit for that one, which came at the end of a long and patient build-up that revealed the extent of Derby's mental exhaustion. As the ball pinged around between the red shirts, the home players could only stand and stare.

"I hope today we started our season," Houllier said. "We haven't been satisfied with the way we've played so far. Today we gave a good team performance. The finishing was good, but mainly the passing and movement were better. I give a lot of credit to the defence, because it's not often you deny any sort of a chance to the opposition. And when you defend well, you can attack freely."

Both Jim Smith, the Derby manager, and Darryl Powell, his captain, used the word "passive" to describe their team's display. "The way Liverpool played today," Smith said, "we had to be at our very best, and we weren't. We were poor in the first half. That's what did my head in. We just sat off them. We felt after the first half if we stepped up we could get back into the game, but they got stronger. And they were very professional. They didn't showboat. They never stopped closing us down. They are good players and if you allow them to knock the ball around you're going to be in trouble."

Derby County: Poom, Powell, Delap, Burley, Johnson, Kinkladze, Christie, Eranio (Sturridge 68), Riggott (Strupar 42), Bragstad, Valakari. Subs Not Used: Morris, Higginbotham, Grant. Booked: Burley.

Liverpool: Westerveld, Ziege, Babbel, Heskey, Owen (Fowler 22), Hyypia, Heggem (Murphy 6), Berger, Barmby (Smicer 81), McAllister, Carragher. Subs Not Used: Arphexad, Traore. Booked: Barmby. Goals: Heskey 17, 54, 67, Berger 80.

Referee: S Bennett (Orpington).