Kerr heads a goal into the net beyond Matildas team-mate Arnold in first goal

Sam Kerr is officially back in business, unfortunately at the expense of her Matildas teammate Mackenzie Arnold after the Aussie duo went head-to-head in their Women's Super League showdown between Chelsea and West Ham.

Kerr scored her first goal of the season in her first full match back, hammering home a header past Arnold as Chelsea crruised to a 2-0 victory at their Kingsmeadow stronghold.

Kerr missed most of the FIFA Women's World Cup and played on one leg during the knockout stages after a calf injury.

The severity of that injury meant that Kerr missed the opening match of the Super League season and came on as a sub against Manchester City last week.

This time around, the 30-year-old showed she is returning to her lethal best with a pinpoint header that had Matildas teammate Arnold clutching at thin air.

It was a relief for Kerr, who has been frustrated by the injury since the end of last season.

'Lovely to be back at Kingsmeadow, back winning & back on the score sheet,' Kerr posted on Instagram.

'Lookin fit too,' her partner Kristie Mewis replied with a winking emoji.

It was an all-too familiar feeling for Arnold, though, with Kerr putting 11 goals past West Ham in seven appearances - more goals than against any other club.

The return to fitness and form of Kerr was a relief for coach Emma Hayes.

Kerr won the Golden Boot title as the league's leading scorer two years running and was Chelsea's leading scorer last season.

Her teammate Fran Kirby is Chelsea's all-time leading scorer and Hayes said it was nice to have both back on deck.

'It's lovely to have those two players and the telepathy we all know, but we need to give them a bit of time,' said Hayes.

'They have only had two training sessions together. We always expect