Miami Open: Eugenie Bouchard and Jelena Jankovic dumped out in Round 1
For the 23-year-old Bouchard, a former World No 5 who has slumped to 56th in the rankings, it was another blow after her first-round exit in Indian Wells.
Miami: Eugenie Bouchard's poor run of form continued on Wednesday as the Canadian suffered a first-round exit at the hands of Australia's Ashleigh Barty at the Miami Open.
Wildcard Barty's 6-4, 5-7, 6-3 win sets up an all-Australian clash in the second round of the WTA hardcourt event against 14th seed Samantha Stosur.
But for the 23-year-old Bouchard, a former World No 5 who has slumped to 56th in the rankings, it was another blow after her first-round exit in Indian Wells.
"It has been a bit of a struggle," said a stone-faced Bouchard, who was unable to account for her loss of form.
Bouchard was a beaten finalist at Wimbledon in 2014 but, apart from a run to the semi-final at Sydney where she was beaten by Britain's Johanna Konta, she has been unable to make an impact this year.
Barty reproduced the gutsy tennis that helped her secure her maiden WTA title at the Malaysian Open in Kuala Lumpur last month.
"We've had a good pre-season and get a good foundation and the stars aligned a bit for us this year so far. We have worked hard and it is just that hard work starting to pay off," said the Australian.
The 20-year-old, who took time out from tennis in 2014 to play cricket, has never come up against her compatriot Stosur before and while she will start as clear underdog, she is relishing the challenge. "It will be good. Obviously we have trained together and hit a lot so it will be interesting. I am really excited. For me it is just another opportunity to go out and play," she said.
Serbia's Jelena Jankovic was another high-profile early exit, the 2008 Miami finalist falling 4-6, 6-4, 7-6 (7/3) to Kazakhstan's Yaroslava Shvedova.
Local favorite and Rio Olympic gold medalist Monica Puig was comfortably dealt with 6-2, 6-4 by Romanian Sorana Cirstea.
The Puerto Rican Miami-resident struggled from the outset and although she battled back well in the second set, Cirstea kept her cool to book a second round meeting with Latvian 19th seed Anastasija Sevastova.
Britain's Heather Watson, who reached the fourth round in Miami last year, was beaten 7-6 (7/4), 6-1 by Romanian qualifier Patricia Maria Tig.
Roger Federer's participation in Laver Cup is in question, though, given his ongoing knee problems.
Muguruza has not managed to string together more than two wins at a tournament and fell out of the world top 10 earlier this month.
Federer underwent three knee injuries in the past two years which led to the 20-time Grand Slam winner announcing his retirement last week.