(Reuters) - A lack of year round consistency is likely to ensure that three-times 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 number one 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 grand slam title by beating Djokovic at the U.S. 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 top of the rankings.

"I don't think so. Right now I'm 31," the world number three 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."

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 number one and was the man to beat at the O2 Arena in south-east London.

"The ranking never lies. He's been winning a lot this year, more than any other player, so he deserves to be number one," 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."

(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by Greg Stutchbury)