Del Potro, Murray provide Miami off-court drama
Britain's Andy Murray (R) is watched by coach Ivan Lendl as he plays a shot during a practice session ahead of the 2014 Australian Open tennis tournament in Melbourne on January 12, 2014 - by Paul Crock
The loss of eighth seed del Potro, still suffering with the left wrist injury that has compromised his season, could deliver a box-office blow to the event with plenty of South American supporters in the Miami area.
"I still feel pain in my left wrist and I don't feel competitive to go on court," Del Potro said. "It's a pity because this is a special tournament for me since there are many Latin fans and Argentines in particular.
"In the next few days I will visit my doctor again to determine the following steps."
German lucky loser Benjamin Becker replaced del Potro in the draw, which has all seeds given byes into the second round.
Del Potro has been troubled by the wrist since injuring it in his opening match at the Australian Open three days after winning the Sydney title in early January.
The former US Open champion has tried to play but with little success, winning one round at Melbourne and reaching a Rotterdam quarter-final before retiring in the first round of Dubai against India's Somdev Devverman.
Murray called it quits with Lendl after a two-year partnership, with a joint statement on Murray's website announcing the move.
"Working with Andy over the last two years has been a fantastic experience for me", said Lendl.
"He is a first class guy. Having helped him achieve his goal of winning major titles, I feel like it is time for me to concentrate on some of my own projects moving forward including playing more events around the world which I am really enjoying."
Under Lendl's guidance, Murray won an Olympic gold medal, the 2012 US Open and last year's Wimbledon title.
"I'm eternally grateful to Ivan for all his hard work over the past two years, the most successful of my career so far," Murray said.
"I’ll take some time with the team to consider the next steps and how we progress from here."
Murray prepares to defend his Miami crown as he continues to return from back surgery.
With seeds absent, Wednesday was reserved for lesser lights fighting for spots in the second round.
Australian Matthew Ebden began with a defeat of Pole Lukasz Kubot 4-6, 6-4, 6-4 while Adrian Mannarino of France beat Russian veteran Nikolay Davydenko, the 2008 champion, 6-4, 7-5.
Spain's Albert Montanes defeated Michel Przysiezny of Poland 5-7, 7-6 (7/5), 6-3.
In a WTA women's field led by defending champion Serena Williams, China's Peng Shuai defeated Czech Karolina Pliskova 7-5, 6-0.
American Vania King blanked Spaniard Estrella Cabeza Candela 6-0, 6-0 while Swede Rebecca Peterson eliminated Germany's Mona Barthel who retired with a stomach complaint while trailing, 6-4, 4-2.
American Lauren Davis, who reached the fourth round last week in Indian Wells, advanced over China's Zhang Shuai 6-2, 6-3.
Austrian Patricia Mayr-Achlietner beat Italian Karin Knapp 3-6, 6-1, 6-4 and Argentine Paula Ormaechea stopped Katarzyna Piter of Poland 7-6 (7/0), 6-1.