Kiki Bertens, the Dutch world number 10, is the latest WTA Tour star to feature in a BBC Sport column. In her piece from the Australian Open, the ninth seed talks about why she used to be scared of playing on the world's biggest courts, facing two-time Grand Slam champion Garbine Muguruza in the last 16 and how changing her coach in the off season has paid dividends in Melbourne.

Once you move into the second week of a Grand Slam, you know you are getting closer to playing on some of the world's biggest courts.

So, after reaching the last 16 at the Australian Open for the first time, I will be on Rod Laver Arena again when I play Garbine Muguruza on Monday.

When I was younger, I was really scared of playing on the big courts.

My first match on a Grand Slam show court was when I played Petra Kvitova on Centre Court at Wimbledon in 2015. Petra was the defending champion and I think I was done in 34 minutes.

A couple of months after that, I played Serena Williams on Arthur Ashe Stadium at the US Open. I gave a better account of myself but lost again in straight sets.

At the time of my career, I didn't like playing on those courts because I was too busy focusing on what the thousands of people in those big crowds were all thinking.

I thought: 'If I don't play good, what will they be thinking? What would they be saying? Will they make jokes about me?'

I was not focusing on myself.

But since then I have grown a lot as a person and a player, and now I've had the experience of playing on the world's biggest courts - Laver, Ashe, Centre and Chatrier.

Nowadays it doesn't matter what court I'm playing on.

I've played on Laver once before; that was a night match against Caroline Wozniacki two years ago and she ended up winning the tournament.

So they are not good memories for me but I am looking forward to playing there again.

Hopefully I will play well and beat Garbine - and then be back on Laver for three more matches this week!

'I watched Muguruza's match - but didn't know I played the winner!'

It is going to be a tough, tough match against Garbine. She is playing much better than last year.

I watched almost all of her 6-1 6-2 win against Elina Svitolina - although I had no idea I had to play the winner!

Garbine played so aggressively and that means I also have to play aggressively, probably more than I have been doing so far in Melbourne.

She came lot to the net, finished her shots well and hit 31 winners.

I lost to her at Indian Wells but it was a good match - I had my opportunities.

From that match, I have learned that I have to keep going for my shots, come to the net where I can and don't let her play too much.

'Clay is my natural surface, so adapting to hard courts took a lot of work'

I'm really happy to have reached the second week at the Australian Open for the first time after beating Kazakhstan's Zarina Diyas on Saturday.

It is also the first time I've reached the last 16 in a Grand Slam on a hard court.

That achievement means a lot to me because you work really hard to perform well in the Slams, especially on a surface that is not natural for me.

Last year I didn't play my best in the Grand Slams and didn't get past the third round at any of them.

I still have a couple more matches to win, though, before I match my best run at a Slam, when I reached the semi-finals on the clay on Roland Garros in 2016.

It has been tough to get used to hard surfaces and adjust my game - I grew up in the Netherlands playing on clay, so I love that surface the most. For my game, it is the most natural.

I have to be more aggressive on the hard court but the biggest thing is the movement. It is so different.

On the clay, I am used to sliding so much and I move really well, but I can't slide on the hard courts.

I don't know how many of the guys do it. I can't do it. So it took a lot of work and a lot of fitness to get there.

I have started to play better on hard courts over the years, so I can be very proud of starting the new season by reaching the second week here.

'My coach's calmness helps me'

One of the big factors in my improved form on the hard courts has been my coach Elise Tamaela.

She took over full-time at the end of last season after I split with my previous coach Raemon Sluiter.

Raemon and I worked together for four years and it went really well in our time together. I moved into the world's top 10 for the first time, reached the Roland Garros semi-finals and won big titles.

I've learned a lot from him.

But I also knew at this stage of my career I wanted to try something different to see if I could go a little bit further and make another step in terms of ranking and titles.

Elise was already part of our team and I felt really positive that she could cover all the pieces in our team, along with my husband Remko, who is my fitness coach and physio.

I get a lot of confidence from Elise. Sometimes when I look at the box, it is just a little nod from her, but I know that means she is saying 'you are doing fine and you know what you need to do'.

She really trusts me to do all the things what we have discussed and make my own decisions on court.

She is a calming influence and that is what I like. Hopefully we can achieve many greats things together.

Kiki Bertens was speaking to BBC Sport's Jonathan Jurejko at Melbourne Park