The British number one spoke to the media following the group stages draw which saw the Scot put in the same group as Roger Federer, Juan Martin del Potro and Fernando Verdasco.
The other group is made up of Rafael Nadal, Novak Djokovic, Nikolay Davydenko and Robin Soderling.
The end-of-season tournament begins on Sunday 22 November, staged at The O2 in London for the first time.
Speaking after the draw was made, Murray said: “In my group Federer is the best in the world, Del Potro has won the US Open and Verdasco has just had his best season to date – there are no easy matches regardless of what group you’re in.”
“At the end of your career you’re remembered for Grand Slams, but to win something like this, you have to beat five of the best players in the world in consecutive matches if you want to lift the trophy which is a very difficult thing to do.”
“You might even have to beat a Federer or a Nadal twice, so it’s a very tough thing to win.”
The final of the tournament will take place on Sunday 29 November.
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BIOGRAPHY: Marcus Rashford