Stan Wawrinka

Murray wins in his debut as the world's top-ranked 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 last week, replacing Novak Djokovic. But the year-end No. 1 ranking is still up for grabs and could be decided on Sunday if both Murray and Djokovic reach the final.

Murray struggled to win his service games in the first set against Cilic, but still ended up saving all but one of the five break points he faced. On the other side, he converted four of his five break...