A hold to 15 for Joao Fonseca, the 28th seed.

Jakub Mensik, the 26th seed, will serve for the first set after the changeover.

What a point! A real 28-shot slugfest of a rally between Jakub Mensik and Joao Fonseca ends with Fonseca going long with a forehand.

30-15 in Mensik's favour - make that the game to the Czech with an ace and an unreturnable serve.

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Joao Fonseca finds a drop-shot winner on game point.

Another break there and he might as well have forgotten all about this first set.

As it is, though, he's far from out of it.

Joao Fonseca with a serve out wide and a forehand winner - deuce.

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At 30-30 on Joao Fonseca's serve, Jakub Mensik steps right in on a second serve, controls the point and has a chance of a double break.

Jakub Mensik loses a point that he was in control of early in his latest service game, but otherwise it's a fairly routine hold to back up the break.

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Three-time French Open champion Alfie Hewett is playing French wildcard Guilhem Laget in the first round of the men's wheelchair singles on Court Suzanne-Lenglen.

Hewett has made a strong start, wrapping up the opening set 6-3 and he's a break up early in the second.

Fellow Briton Gordon Reid lost in straight sets to top seed Tokito Oda, the three-time defending champion, earlier today.

But Joao Fonseca goes just wide into the tramlines with another forehand and the first break of the match goes Jakub Mensik's way.

An overhit forehand by Joao Fonseca sails long and gifts Jakub Mensik two break points.

The first is saved...

A couple of deuces but no break-point chances for Joao Fonseca and Jakub Mensik holds.

BBC Radio 5 Live

As Jakub Mensik is taken to deuce at 2-1 in the first set, a reminder that you can listen to live coverage from Roland Garros on BBC Radio 5 Live and BBC Sounds - and also by clicking on the link at the top of this page.

There's also a daily podcast from the team in Paris available via BBC Sounds.

Joao Fonseca is aiming to become the fourth man from Brazil to reach a Grand Slam semi-final, after Ron Barnes, Fernando Meligeni and Gustavo Kuerten.

Kuerten got to the semi-finals at Roland Garros three times and on each occasion he made it that far, he went on to win the title - the most recent of those being in 2001.

Kuerten watched from the stand as Fonseca beat Casper Ruud in the previous round and he's there again tonight.

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Joao Fonseca falls 0-30 down on his serve but smacks away a forehand winner and a smash to avert any imminent danger.

It remains on serve early in the first set.

If Jakub Mensik wins tonight, he'll become the first Czech men's semi-finalist at a Grand Slam since Tomas Berdych got to the last four at Wimbledon in 2017.

A couple of errors by Jakub Mensik in the Czech's first service game leave him 15-30 down.

Two consecutive aces bring up game point and he wraps up the hold.

Four straight points for Joao Fonseca and the 19-year-old Brazilian holds serve against the 20-year-old Czech.

Joao Fonseca, cheered on by several in yellow Brazil shirts inside Court Philippe Chatrier, serves first in the quarter-final.

Very much looking forward to this.

There was also a men's quarter-final between a 20-year-old and a 19-year-old at Roland Garros 20 years ago.

On that occasion, 20-year-old Rafael Nadal progressed against 19-year-old Novak Djokovic.

Just the 46 Grand Slam singles titles between those two.

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The two players have arrived on Court Philippe Chatrier and they're about to begin their warm-up.

Jakub Mensik and Joao Fonseca have played each other only once before and that was at the 2024 Next Gen Finals, in which the best players aged 20 and under compete.

The format was slightly different for that event, with sets won by the first player to reach four games.

All five sets of their round-robin match went to tie-breaks and Fonseca won it, before going on to win the title.

Jakub Mensik might be slightly the fresher of the two players in this night-session match. He has been on court for exactly 13 hours during this tournament, compared to Joao Fonseca's 14 hours and 29 minutes.

Mensik has come through a couple of five-setters - he collapsed on court with cramp immediately after his second-round win, which he completed in four hours and 41 minutes at the height of the Paris heatwave.

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Fonseca went all the way in his third-round win against Novak Djokovic, finishing in just shy of five hours, while he was on court for nearly four hours in his four-set victory over former French Open runner-up Casper Ruud on Sunday.

The cooler temperatures in Paris over the past couple of days, and of course the roof being shut on Court Philippe Chatrier, will only help the players as they dig further into their physical reserves.

There was even a hailstorm at Roland Garros earlier on. It's June!