Indian Wells: World number two Andy Murray slumped to a shock 6-4, 4-6, 7-6 (7/3) defeat to Argentina's Federico Delbonis in the third round at Indian Wells on Monday.
Murray was playing in his first ATP Tour tournament since losing to world No 1 Novak Djokovic in the final of the Australian Open in January.
"It was a tough one to lose," Murray said. "I fought hard to get into a winning position.
"I couldn't go for my shots and when I did I made mistakes."
Murray, who became a father on 7 February with the birth of his daughter Sophia Oliva, looked rusty Monday after his layoff.
His downfall was an inability control the match with his serve and volley. Delbonis was much stronger in the longer rallies in the first career meeting between the two.
Murray's forehand on match point sailed well wide and long, ending the two hour, 46 minute contest on Stadium Court.
"He came up with some good passing shots. I could have done a bit more with the volleys and my serve," Murray said. "He moved better than what I expected."
Delbonis has been one of the busiest players in 2016 and it showed as he used a variety of shots to keep Murray off his guard. Indian Wells was his sixth tournament of the season.
"In the end it was a question of can I do my job? This is what I get," Delbonis said.
This is the first time Delbonis has beaten a player ranked as high as Murray, but not the first time the claycourt specialist has knocked off a top five powerhouse.
In 2013, he upset Swiss superstar Roger Federer in the semi-finals of a clay court tournament in Hamburg, Germany.
Delbonis advanced to the fourth round of the ATP and WTA hardcourt event, where he will face either Gael Monfils of France or Spain's Albert Ramos-Vinolas.
Murray looks to Miami
The 28-year-old Brit Murray said he is now looking forward to the next stop on the ATP Tour in Miami, which he uses as a training base and where he will be reunited with his family.
"I will see them in a couple of days," he said.
"I am not concerned about my tennis. I do think I will play better tennis in Miami because I played some good stuff in the Davis Cup."
Canada's Milos Raonic barely had to break a sweat against Australian Bernard Tomic, who retired early in the second set with a wrist injury.
Raonic is trying to improve on his previous best performance in Indian Wells, a semi-final loss to Federer last year.
The 25-year-old Canadian was up 3-0 in the second set in the third round tie, after cruising through the first at 6-2, when Tomic called it quits.
World No. 14 Raonic blasted nine aces and won 91 percent of his first serve points in 36 minutes on the court. It took him just 25 minutes to win the first set.
His quarter-final win over 14-time Grand Slam winner Rafael Nadal last year at Indian Wells was voted one of the best matches of 2015.
Raonic claimed his eighth career singles title by winning in Brisbane earlier this year.
In women's action, Czech Karolina Pliskova subdued former world No. 1 and 2008 Indian Wells winner Ana Ivanovic 6-2, 6-0.
The assault on the women's top seeds continued with the elimination of Swiss seventh seed Belinda Bencic, who lost to Slovakia's Magdalena Rybarikova 6-4, 3-6, 6-3.
Johanna Konta rolled to a 6-4, 6-1 win over Denisa Allertova, who sent women's second seed Angelique Kerber crashing out on Saturday.
Just three of the top seven women's seed are left in the draw, including world number one Serena Williams.