There's applause from the crowd as the fan is helped from the court by medical personal.

Canadian third seed Felix Auger-Aliassime is on serve to get us back under way on Court One, and he goes on to hold with little resistance, sealing it with an ace.

Tracy Austin
Two-time Grand Slam champion on BBC One

It is so unusual to see Aryna Sabalenka feeling so much pressure on the return as well. She must've thought: 'I'm feeling getting the second serve that I can hit', but she is struggling to get it back in play.

She is used to doing that to her opponents, not the other way round.

Naomi Osaka took a little time to find her feet on first serve at the start of this match but a 111mph effort out wide gets her to 30-0.

Osaka races to a hold to love.

Tracy Austin
Two-time Grand Slam champion on BBC One

I actually love that tactic from Aryna Sabalenka. I'm told by people that were watching her in practice that she has been practicing the serve and volley.

However, I wouldn't suggest doing it all the time because then Naomi Osaka gets a target and knows she's coming in. But sporadically mixed in, that will work.

Amy Lofthouse
BBC Sport at Wimbledon

There’s a cheer for Aryna Sabalenka as she arrives at the baseline after holding for love.

I feel like the crowd are more in favour of Naomi Osaka but they’re willing Sabalenka to turn this into a contest.

Naomi Osaka thinks she has levelled at 15-15 with a backhand down the line but it's called out and there are gasps from the crowd when replays show just how close it was. Fine margins.

Sabalenka gets a very important hold when Osaka's forehand arcs wide and into the tramlines.

We've got a short delay on Court One as someone in the crowd is seen to by medical personnel. Fingers crossed it's nothing serious.

Felix Auger-Aliassime and Alejandro Davidovich Fokina are taking the opportunity to hydrate at court-side, with the pair still on serve at 1-1 in the third set.

Aryna Sabalenka is back and will be hoping to put that first set firmly in the past.

The top seed is on serve to begin the second set. A great chance to start with some positivity.

Tracy Austin
Two-time Grand Slam champion on BBC One

Naomi Osaka was really able to just suffocate Aryna Sabalenka there. She wasn't letting her opponent even get into the points. Sometimes, as a player, it is really difficult when you don't feel like you're making any impact at all because your opponent is playing so well.

If you're Sabalenka, you've got to change something up. She needs to add in some variation and a few more slices.

Image source, Reuters

Sam Smith
Former British number one on BBC One

An immaculate set of tennis from the four-time major champion. Naomi Osaka takes this opening set at a gallop.

With all that rummaging around, you would suspect top seed Aryna Sabalenka is off for a break.

Naomi Osaka has decided to stay out on the court and is going through some exercises - kicking her legs up into the air and doing some gentle shuttle runs up and down the line - to ensure she stays loose.

Amy Lofthouse
BBC Sport at Wimbledon

Not surprisingly, Aryna Sabalenka is heading off court.

Novak Djokovic did say that they were battling the wind on Centre Court earlier - and Sabalenka has come unstuck in those conditions before.

That was just brilliant from Naomi Osaka, though. More controlled than her opponent, hitting hard and serving well.

Naomi Osaka gets the hold and takes the set at the first time of asking when Aryna Sabalenka finds the net.

Osaka has been so composed.

Image source, Getty Images

Naomi Osaka wants this set wrapped up.

She brings up two set points with an ace as the paint skips up off the grass.

Tracy Austin
Two-time Grand Slam champion on BBC TV

It looks like there's a bunch of racquets that are coming down out of the Aryna Sabalenka camp.

I can see four or five in her coach's hand. I would suspect she wants a racquet that is strung tighter. There might be some that she has strung 1lbs or 2lbs tighter, and the tighter you go the more control you have.

She is looking at them now and deciding which one she wants to go to.

One of Aryna Sabalenka's coaching team has just walked down to the side of the court to hand over four racquets at the change of ends.

Sabalenka is yet to get one of them out yet but looks set to make the switch at the end of the set.

Amy Lofthouse
BBC Sport at Wimbledon

The serve and volley is a nice change of pace, but Sabalenka looks a bit stunned.

She’s used to doing this to opponents, not having it done to her…

Aryna Sabalenka realises that her gameplan isn't working and looks to change up her approach. A serve volley gets Sabalenka up and running before a drop shot takes her to 30-0.

An emphatic forehand winner seals the hold to love.

It's probably too little too late for this first set but there's still a long way to go in this match.

Tracy Austin
Two-time Grand Slam champion on BBC TV

This is absolutely the best we've seen Naomi Osaka since she came back. She probably thought it was taking way too long, and actually most of us were thinking it because this time last year she wasn't even ranked in the top 50.

She has done a great job of getting more consistent in her tournaments, she is fitter than I've ever seen her and she is so committed to being controlled out there.