Friday is the day Sam Kerr joins Chelsea as the mid-season transfer window opens, the arrival of the player I consider the best No 9 in the world ending an amazing year for women’s football.

It has been a year of massive strides. The World Cup was huge and Megan Rapinoe brought positive attention to the women’s game by being brave and speaking about important topics while also doing her talking on the pitch. There have been big signings and groundbreaking sponsorship and broadcasting deals. Clubs playing in men’s stadiums has become normalised and crowds of 30,000-plus have turned up for league games – there has been one incredible moment after another. After the World Cup the only worry was whether that momentum could be carried forward and I think that has been achieved.

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It will be harder to maintain that growth in 2020, without a showpiece event for the women’s game. There will be the Olympic Games but because it is not solely about football and it is being played in Tokyo, a long way away with an inconvenient time difference – the women’s final kicks off at 3am BST – it will very easily get lost. The 2012 Games were a real gamechanger for women’s football but this time excitement may not build unless Team GB look likely to win a medal.

There is so much to look forward to before then, including a potential WSL title decider just a few weeks into the new year when Chelsea travel to Arsenal for what may end up being Kerr’s debut. She is likely to need an adaptation period. She is good enough to hit the ground running but this is a player who has never played in Europe and who has been playing in America where there is more of a transitional game, with a greater reliance on athleticism and less of a tactical approach.

But Chelsea can’t really afford to sit around waiting for her to hit her stride. After beating Manchester City at the start of December they could manage only a draw at struggling Liverpool in their last game before the winter break, and now the pressure is really on them. They are third in the league, four points behind Arsenal, and even with a game in hand their margin for error is slender. Defeat against an Arsenal team that have lost once all season will significantly dent their title chances.

But even if Kerr’s arrival doesn’t immediately turn Chelsea into champions, it is a massive moment for the women’s game in the UK. She has become a symbol of the Women’s Super League’s progression and potential and, like when David Beckham moved in the other direction and massively increased the amount of global attention MLS enjoyed, Kerr’s arrival means people around the world will be interested in what is happening here.

Chelsea and the WSL in general will enjoy commercial opportunities, and though the league was already moving in the right direction suddenly that momentum can accelerate. It will be interesting to see how much thought has gone into marketing her arrival: will Chelsea try to tap into the big Australian community in west London? Will Nike, which sponsors Kerr and Chelsea, put its might behind the move, like Adidas did when Paul Pogba rejoined Manchester United?

Facebook Twitter Pinterest Vivianne Miedema scores for Arsenal against Reading. Photograph: Gavin Ellis/TGS Photo/Rex/Shutterstock

Also interesting will be the impact of her arrival on Vivianne Miedema, who has been a phenomenon at Arsenal for the last couple of years but now finds her position as the league’s marquee player under threat. Miedema is a European champion and World Cup finalist and her goalscoring record has been immense but if I were forced to choose between the two I would say Kerr edges it, because of her pace, dynamic movement and her ability to frighten defenders. Miedema is supreme in the penalty area but Kerr’s movement around it is a constant threat.

Neither player was in the Ballon d’Or top three but they will have been rightly disappointed not to have been in that conversation and in 2020 we will have two players in England whose ambition will be to prove themselves the world’s best forward. Though I wouldn’t compare them as players to the men, it could be something like the Messi v Ronaldo battle while they were at Barcelona and Real Madrid: two outstanding players at rival clubs, pushing each other to ever greater levels of performance and achievement.

For those who have not seen much of Kerr, I would compare her to Jamie Vardy. She is especially brilliant on transitions: when a midfielder gets the ball and has the ability to pass between or over defenders, that is when she comes alive. When there is room for her to run in behind a defence, she is the best in the world by far. Her movement is very good, she is always active across the line of defence, and when she gets in behind she is deadly. She can finish with either foot and is great in the air for someone who at a shade under 5ft 6in is not exactly tall.

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She is a bit like her compatriot Tim Cahill, in that her ability to score with her head is constantly surprising. Watching Chelsea’s game against Manchester City this month it was striking how many counterattacking moments they had, without finding the right pass in transition. Kerr’s arrival will make them so much more dangerous at these moments – so long as her teammates find the right pass. In the World Cup you also saw a player who was capable of bearing the responsibility of leading – and in many ways carrying – a team: scoring the goals, taking penalties.

It will be interesting to see whether any of the other WSL teams feel pressured into making moves during a transfer window that tends to be very quiet in the women’s game. Kerr’s arrival shows not only that some WSL teams can pay big money for the right players but that in comparison with Spain – where there are some good teams but the league as a whole is struggling – or Italy – where clubs would have been unable to afford her – or France – where Lyon win every year by a mile and there is no real challenge – or Germany – which is seen as a very demanding league that can be difficult for foreign players to acclimatise to – England now has a case for being considered the ideal destination for the best players in the world.

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