French Open boss backs line judges after fan spots missed call

Tennis balls leave impressions on clay courts unlike other surfaces. (Getty Images: Julian Finney)

The French Open is the only tennis grand slam that still has people, rather than machines, calling its lines.

A controversial missed call cost Casper Ruud a set point in his five-set loss to Joao Fonseca in the fourth round.

Roland Garros director Amelie Mauresmo says neither people nor ball-tracking technology is 100 per cent accurate.

French Open director Amelie Mauresmo has backed her line judges, saying she has no immediate plans to introduce the technology at Roland Garros despite a controversial call during Casper Ruud's loss against Joao Fonseca.

Ruud, a two-time runner-up in Paris, ultimately lost the fourth-round match 7-5, 7-6(10/8), 5-7, 6-2, but during the second-set tiebreaker, with Ruud up 8-7, a spectator in the crowd shouted that a forehand down the line hit by Fonseca had landed out.

The chair umpire came down to check the mark and ruled that the Brazilian's shot was in, handing him the point.

An electronic line-calling on television showed the ball was out, but the Parisian tournament does not use the ball-tracking technology like the other grand slams, with tradition-obsessed Wimbledon last year joining the Australian and US Opens in ditching line judges.

Mauresmo said after the match that she still prefers humans over technology because it cannot be entirely trusted.

"What we observed at the clay-court tournaments leading up to Roland Garros is that the reliability of this system is not absolute," she told reporters.

"As of today, the machine is not 100 per cent reliable, so we continue to place our confidence in human officials."

French Open director and former world number one Amelie Mauresmo. (AP: Michel Euler, file photo)

The WTA and ATP have added machine-generated rulings for red-clay events, but Grand Slam hosts make their own rules.

Although disputes over marks on the surface are not rare at Roland Garros, Mauresmo said many players recognise the system is not entirely reliable on clay, a live surface that constantly changes with weather conditions and poses challenges to accurate digital tracking.

"So we have received no real feedback pushing us in that direction [of electronic line-calling]," she said, adding that there will be a review after the tournament.

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"For us today, what matters is reaffirming our trust in human officials. We've made that choice