Serena Williams went along to support her sister Venus, while a grieving Steve Johnson was in tears as his opponent Borna Coric had a meltdown after his French Open exit and chair umpires were in the wars on day four.

A pregnant Serena was in her older sister's box at Roland Garros and the 10th seed put on a show to beat Kurumi Nara 6-3 6-1 in the second round on Court Philippe Chatrier.

Serena chatted to her coach, Patrick Mouratoglou, as Venus went about her business, possibly plotting how she might win grand slam title number 24 once she has given birth.

Johnson could not hide his emotion after winning a highly-charged encounter with Coric just a few weeks after his father, Steve Snr, passed away suddenly.

A chair umpire went crashing to the deck before another was struck by a stray Robin Haase backhand on an eventful Wednesday in Paris.

'GOOD JOB' IS SERENA'S VERDICT ON VENUS WIN

Serena had to take a back seat on the big stage with a baby on the way, but there was no keeping her away from the second major of the year.

Venus was a cut above Nara and Serena was clearly impressed.

The senior sibling revealed: "She said 'good job'. Yeah, and she came in sometime during the match. I don't know exactly when.

"I'm sure she feels the excitement of being at a major and not having the pressure to play and prepare. Must be an interesting feeling to say the least. But she knows exactly what it's like out there, and she's had a lot of success here. If she stays here through the end, I would like that."

COURAGEOUS JOHNSON VOWS TO FIGHT ON, CORIC APOLOGISES

It was by no means all about the action on the show courts as emotions ran high on Court 6.

Johnson broke down in tears after showing incredible character to oust Coric in a four-set tussle, during which the California native was docked a point for ball abuse and asked the match referee to intervene.

"I know it's going to be emotional for quite some time. I just know he was with me. He raised me to be a competitor and a fighter until the last point," Johnson said. "I may not be the best tennis player but I will always fight."

Coric repeatedly smashed his racket into the clay after bowing out and later apologised, saying: "I was on the court for four hours. And it's not something which should be my excuse, but, you know, I got mad.

"I think everyone gets mad from time to time. Maybe I didn't show it in the right way but - I made a mistake, but that's it."

OFFICIALS IN THE WARS ON CHATRIER

Officials are accustomed to not getting any sympathy and it was no different on Court Philippe Chatrier on day four.

A big crowd roared with laughter after the chair umpire jumped down to check a mark in the clay at a key moment in the second set of Garbine Muguruza's win over Anett Kontaveit and went sprawling on the red stuff.

He got back on his feet to perform his duties and took a hugely embarrassing moment on the chin, saying 'merci' over the microphone after a round of applause.

Arnaud Gabas was later hit by a shot from Haase in his loss to Rafael Nadal, prompting the man from the Netherlands to pretend to fire a bow and arrow at him. 

Thankfully there was not much power on Haase's shot, as the same official took a nasty blow from Denis Shapovalov back in February which left him with a fractured orbital bone.

SOCK PUTS HIS FOOT IN IT

While all that drama was going on a group of American supporters told me they had travelled to Roland Garros with high hopes of Jack Sock making it into the second week.

Unfortunately he had already got off on the wrong footing, as he was sent packing in the first round.