One mistake can turn any match, as Andy Murray discovered to his cost. What was galling for the 26-year-old Scot was that it was not his error that put Novak Djokovic on the way to a 7-5, 6-3 victory in their quarter-final at the Miami Masters but the umpire's.
Both men had been at the top of their form in a first set of the highest quality until Murray served at 5-6. On the opening point Djokovic had what looked to be an easy put-away at the net, but clearly had his racket on Murray's side of the court when he hit the ball. When the point was replayed on the big screen Murray complained to the umpire, Damian Steiner, who insisted, contrary to the video evidence, that the point of contact had been on Djokovic's side of the net.
Murray, having lost his focus, promptly made three backhand errors in succession as Djokovic broke to love to steal the set. It was cruel on Murray, though the Scot's response at the start of the second set was excellent.
Bristling with aggression, Murray hit a succession of bold groundstrokes to break serve in the fifth game. However, as he has done on too many occasions in the past, Murray followed a break with a poor service game of his own, two double-faults and a poor backhand enabling Djokovic to level the score at 3-3.
The match quickly slipped from Murray's grasp from that moment onwards. Djokovic held for 4-3 and then broke his long-time rival to love as the Scot's errors multiplied. The world No 2 went on to serve out for victory after an hour and 30 minutes with another love game.
Djokovic has now won 12 of his 20 meetings with Murray. This was their first meeting at the quarter-final stage of a tournament for six years, which is one of the prices Murray has paid for falling to No 6 in the world rankings. He is likely to drop further next week.
If there was disappointment at his continuing failure to beat a top-10 opponent – Murray has not done so since he beat Djokovic in last year's Wimbledon final – there are positives that the Scot can take from his performances at one of his favourite tournaments.
The Scot has a second home in Miami, which is also his training base. He is familiar with both the courts at Crandon Park and the hot and humid conditions, though Djokovic is equally at home there. Between them the two men have won five of the last seven Miami tournaments.
Murray's form had been patchy since he began his comeback three months ago following back surgery, but there has been an upturn in his form in Miami, despite the disappointment of his split with coach Ivan Lendl, who turned up once again to support his former charge.
The Scot needed pain-killers after appearing to hurt his left hip in his previous match 24 hours earlier, but there did not seem to be any problems with his movement this time.
Djokovic has also run into form this month, having claimed his first title of the year in Indian Wells 11 days ago. The world No 2 goes on to face the winner of the match between Roger Federer and Kei Nishikori.