Tomic's woes continue in Miami

Bernard Tomic is in danger of tumbling out of the world's top 50 after his season from hell continued at the Miami Open.

Without a win since the Australian Open, Tomic was forced to withdraw from his scheduled first-round match at tennis' so-called "fifth major" on Friday (AEDT) with a back injury.

The tournament was Tomic's last hardcourt opportunity before the European clay season gets underway next month.

Tomic has suffered seven straight first-round defeats on the ATP Tour since last year's US Open, his most recent victory coming against the 115th-ranked Ryan Harrison in Shenzhen last October.

But, in a worrying sign, the 24-year-old's record on clay is even worse.

Tomic has lost eight consecutive ATP matches on dirt over the past two years, with his first-round victory over world No.662 Brian Baker in Roland Garros 10 months ago his only success on the surface in 2016.

Entrenched inside the top 20 for much of last year, Tomic must now wait until June before hitting his preferred grass courts.

But unlikely to be seeded following his barren run, the Australian No.2 will be at the mercy of the draw as he defends a swag of rankings points from reaching the round of 16 at Wimbledon.