A lack of year-round consistency is likely to ensure three-time grand slam champion Stan Wawrinka does not topple Britain's Andy Murray from the top of the rankings, the Swiss has said.
Murray recently ended Novak Djokovic's 122-week spell as world No.1 but might still need to win the final ATP tournament of the year in London to ensure he finishes the year at the top of the rankings.
Wawrinka, who won his third major by beating Djokovic at the US Open this year, has been drawn in the same group as Murray at the ATP Finals, but feels he does not have the consistency to leap to the rankings' summit.
"I don't think so. Right now I'm 31," world No.3 Wawrinka told Sky Sports when asked whether he could become the top-ranked player.
"I know I can beat every player, I need to do it more often in the year if I want to think about that but, so far, I'm way off that."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Wawrinka expected the 29-year-old Scot, who won Wimbledon and his second Olympic gold medal as well as six other titles this year, would handle the pressure of being No.1 and was the man to beat at the O2 Arena in southeast London.
"The ranking never lies. He's been winning a lot this year, more than any other player, so he deserves to be No.1," Wawrinka added.
"He did really well with the pressure ... so he knows how to deal with it.
"I'm sure he would love to win the world ATP title here in London.
"I think every player tires at the end of the year but, if you look at the last few tournaments, he's in top form - a lot of confidence to take to this tournament here so he will be tough to beat."
