Briton Andy Murray believes November's end-of-season World Tour Finals in London could become a straight fight for the world number one spot.
Murray, who today was confirmed by the ATP as a qualifier for the event featuring the world's top eight players, rose to number two in the rankings on Monday after claiming his fifth title of the year at the Masters event in Montreal.
World number one Roger Federer, aiming for a sixth consecutive U.S. Open title later this month, and Spain's Rafael Nadal, ranked third in the world, have already qualified for tour finale which is being held in London for the first time.
"I think there could be a battle for the number one in the world," Murray, who could face Federer in the semi-finals of the Cincinnati Masters this week, said in an ATP statement.
"That's what everybody hopes for. This year the Tour is very tough and it's tight at the top. Hopefully that's what we'll get to see. It's great to qualify. Obviously with it being in the UK this year, it's big for me."
Murray's victory over Argentina's Juan Martin del Potro in the Montreal final meant that he ended Swiss Federer and Nadal's four-year domination of the top two places in the rankings.
Federer, winner of the French Open and Wimbledon this year, leads the rankings with 11,040 points to Murray's 9,250 with Nadal, who has just returned from a knee injury, on 8,665.
An early defeat for Federer at Flushing Meadows, and a long run for Murray, could see his top spot come under threat from the in-form Scot.