Andy Murray eased into the quarter-finals of the BNP Paribas Open in Indian Wells after fourth-round opponent Nicolas Almagro was forced to retire with an ankle injury.

Fourth seed Murray was leading 6-2 1-0 when his unseeded Spanish opponent was forced to call it a day having already called a medical time out at the end of the first set.

Next up for Murray is a tricky looking encounter with sixth-seeded Swede Robin Soderling, who defeated Jo-Wilfried Tsonga in straight sets to reach the last eight.

There were few indications of any physical weakness in world number 40 Almagro at the start of the match as he hit a number of strong winners on his way to forcing an early break of the Murray serve.

The Scot rallied with a break to love in the next before moving firmly into the driving seat with another break as mistakes began to litter Almagro's game.

Almagro won just 33% of points on his own serve and hit 16 unforced errors in what was a scrappy first set for the Spaniard, who conceded a third break in the eighth to hand Murray a one-set lead.

The 24-year-old called for treatment to his left ankle at the end of the first set, and though he battled on, Almagro offered his hand after Murray held his serve in the next game.