Andy Murray wins in debut as world's No. 1 player

Taking the court as the No. 1-ranked player for the first time, Andy Murray got the job done. 

The Wimbledon champion was tested for much of his opening match at the ATP finals but still came out on top, beating Marin Cilic 6-3, 6-2 Monday at the O2 Arena. 

Murray took over at the top of the rankings...