Andy Murray has never been one to shirk a challenge, but the Scot may just have breathed a small sigh of relief yesterday when he was given a walkover into the fourth round of the Sony Ericsson Open in Miami.

The world No.4 had been due to take on Milos Raonic, the man whose outstanding serve has earned him the nickname 'The Missile' but the Canadian pulled out of their match due to an ankle injury. Raonic, ranked No.26 and one of the brightest prospects in the sport, suffered the injury in practice and lasted just three games of his doubles match the previous night.

It improved a little overnight but the 21-year-old decided his ankle was not strong enough to risk singles against Murray, whose range of shots and fitness promised to provide Raonic with a gruelling test, even before the injury. While Murray would probably have enjoyed trying to figure out the Raonic serve, he will also be looking forward to his next match tomorrow against Gilles Simon, after the Frenchman defeated Austria's Jurgen Melzer 7-6, 6-4 in their third round tie last night. Murray can afford to be confident ahead of the meeting having won eight of their last nine matches.

However, while the Scot was enjoying an extra bit of rest yesterday, two other Britons were soaking in the atmosphere of an arena in which they are beginning to belong. Scotland's Colin Fleming and Englishman Ross Hutchins will today compete for a place in the quarter-finals of the doubles event, taking on Leander Paes and Radek Stepanek.

It is another step in their quest to earn a spot in the season-ending Barclays ATP World Tour Finals at London's O2 in November, for which the top eight teams qualify. They are 11th after a good start to 2012.

Although they were beaten in the first round in Indian Wells – by Andy and Jamie Murray – quarter-final appearances at Wimbledon and the US Open last year showed they can compete with the best.

Miami is only Fleming's second Masters 1000 event but he and Hutchins, who has slightly more experience having partnered Andy Murray occasionally in the past, are starting to believe it too.

"We feel like we're backing up the wins with consistent results as well," Fleming said. "Playing at these kind of tournaments with these people gives you confidence in itself, being here and seeing the way these people play. We're working hard to make it a constant for us to be at these the whole time."

Being there is half the battle – the extra ranking points at Masters 1000s are invaluable – but they are not content simply to make up the numbers.

"We want to establish ourselves," Fleming said. "We've spoken a lot about wanting to make the World Tour Finals. If you're going to make that, you're going to have to get results in the Masters Series."