McCartney Kessler plants a volley into the net before Aryna Sabalenka's forehand winner gives the top seed an early two-point cushion.

Nuno Borges is looking very solid on serve, holding to 15.

Despite a couple of fine McCartney Kessler winners, Aryna Sabalenka does enough to hold and take this set to a tie-break.

Marion Bartoli
Former Wimbledon champion on BBC Two

You need to be willing to take more risks. In the second set Kessler is a metre further forward on average with her hit point.

It is not easy to do against a player like Sabalenka. You really need to be on it with your footwork.

Jeff Tarango
Former American tennis player on BBC Radio 5 Live

The number one player in the world should exude a lot more confidence than Aryna Sabalenka, in my opinion.

She should be a lot more secure in herself. She shouldn't have to turn around to her box and whine and cry every other point. She should be looking down at the ground and focused on her strings, the tennis ball and her opponent.

She should not be being reaffirmed by her coaching box. It makes no sense to me. It is going to hurt her in the long run because her opponents know she is going to crack at some point.

Image source, Getty Images

That's a much more positive approach from Nuno Borges, who is starting to attack Jannik Sinner's serve, but the Italian comes through deuce unscathed.

Aryna Sabalenka swings her racquet in irritation as a couple of returns go long.

McCartney Kessler then seals the hold as Sabalenka gets the return wrong again and plants it into the net.

Sabalenka must now serve to take this set to a tie-break.

Nuno Borges opens the second set with some spirited defence, pulled from corner to corner across the baseline, but ends up with his shoulders slumped after netting a backhand.

He earns the applause of the Centre Court crowd with a flicked backhand winner from the baseline before gobbling up a poor drop shot for 30-all.

The pair trade points for 40-all - the first challenge to Jannik Sinner's serve.

Two-time Wimbledon semi-finalist Daniil Medvedev has already had a few questions to answer in the early stages of his match with Daniel Merida on court two.

It remains on serve after four games of the first set, but Russia's Medvedev, seeded eighth, had to save two break points in his opening service game.

Pat Cash
Former Wimbledon champion on BBC Radio 5 Live

Full credit to Nuno Borges. He has been playing really well and he has been serving extremely well. He is keeping Jannik Sinner on the back foot.

He served at 77%, which is a great service percentage. He hits the ball very flat, after growing up playing on the clay, so it is coming through the court really nicely. His backhand down the line and cross-court has been absolutely brilliant as well.

Sinner and his team will be really relieved to get away with that one. You would expect him to put the hammer down here, but it is going to be a tough second set.

From being on the brink of losing the second set to drawing level with a hold to 15.

It feels like the momentum is on Aryna Sabalenka's side again.

What has McCartney Kessler got in response?

Emily Salley
BBC Sport at Wimbledon

Image source, Getty Images

That was probably tighter than Jannik Sinner would have hoped for, but he avoids falling a set down early doors like he did in his first round match against Miomir Kecmanovic.

The Italian turns to his team, shakes his fist and then struts back to his chair, looking confident.

Amy Lofthouse
BBC Sport at Wimbledon

That Sabalenka return was hit fast and hard and for all the world looked like it was going long. Kessler didn’t even move to return it.

This next service game could be interesting for Sabalenka. She’s cranked the noise up a level to try and spur herself on, but she’ll need to hold relatively sharpish to keep Kessler at bay.

Image source, PA Media

That's magnificent from Aryna Sabalenka as a powerful backhand return winner seals the break back after dominating the previous point in a rally.

Kessler is made to pay for not taking those two set points.

Jannik Sinner closes out the opening set at the first opportunity.

Coming on the approach, he hammers a forehand deep into the corner on Nuno Borges backhand and although the 29-year-old puts in a good scramble, all he can do is get his frame on it.

Borges was hanging in a little at the back end of the tie-break. How will he respond?

Huge second serve from Jannik Sinner to tee up set point.

Jannik Sinner earns the mini-break with a deep return which Nuno Borges returns into the net.

His eyes light up as the court opens up for a backhand pass for set point but his shot clips the net cord and pings into the tramlines. But, the Italian is two points away from taking the first set.

McCartney Kessler chooses the right time to come into the net and force Aryna Sabalenka into a mistake.

She can't take her second set point however, as she overcooks a forehand.

Jannik Sinner eases through two points.