UPDATE: Rafael Nadal pulled out prior to the match, due to his knee injury, allowing Andy Murray to progress to the Miami final.
Below are a few links to free TV streams - ikerversusnadal.com does not host these streams and does not take responsibility for the legality of the linked sites.
Miami – Links to Free Live TV Streams
Rafael Nadal vs Andy Murray, Friday second match, probably after 4pm (8pm GMT)
Option 1 – Miami – Live TV – English
Option 2 – Miami – Live TV – English
If none of these are working, or to find one that works better, check the listings at RojaDirecta, Atdhe, Sport Lemon, Live Score Hunter

Where have you got your facts from? The head-to-head is 13-6 and Murray won their last match in Tokyo, not at the World Tour Finals where they were in different groups and never met.
GO RAFA!!!!!!!!!!!!!!!!!!
Hi Advait, you are half right, and I have corrected that the last match (won by Murray) was indeed played in Tokyo. According to the ATP stats however, the head to head does stand at 13-5: http://www.atpworldtour.com/Players/Head-To-Head.aspx?pId=N409&oId=MC10
Hope you didn’t get a flash vision of the future?