Tennis line judges face an uncertain future after the ATP announced that they will be replaced by "electronic line calls" at this year's inaugural Next Gen Finals in Milan.
For the first time at an ATP event, the chair umpire will be the only official on court, with Hawk-Eye Live technology used to judge whether shots are in or out.
Decisions will be final with players unable to challenge calls as they do at most tournaments via Hawk-Eye playback.
Marginal calls will, however, still be accompanied by a visualisation on video screens around the stadium.
Foot-faults, usually called by judges positioned in line with the baseline, will be determined by a 'review official' who will monitor the feet of servers via cameras.
The Next Gen ATP Finals in November, which will be contested by the top eight players aged 21 and under, will feature a range of new innovations including a shot clock and short sets.
Electronic line calling, however, raises the possibility of judges being phased out for good, ending the ritual of players scowling at officials when decision go against them.
"This could be a landmark moment for officiating in our sport," Gayle David Bradshaw, executive vice president of the ATP's Rules and Competition department, said.
"Our athletes work incredibly hard and they deserve the very best and most accurate officiating we can offer. The technology is now in a place where we feel comfortable trialling this new system in a real tournament environment."
Hawk-Eye Live technology has been tested for 18 months and Sam Green, Director of Tennis at Hawk-Eye, believes it will become "the future of tennis officiating".
"Working with the ATP has allowed us to refine the system to not only improve the quality of line calling, but the overall fan experience," he said in a statement.