Andy Murray's coach Ivan Lendl has warned the Scot of the challenges that he will face next year.

Murray won his first Grand Slam as well as Olympic gold in 2012, but Lendl believes that it will be even tougher for the 25-year-old next season.

With Rafael Nadal returning in January, competition at the top of the men's game will increase further.

"Tennis is a very difficult sport to win these days," said Lendl. "With the likes of [Novak] Djokovic, [Roger] Federer and Nadal, and Andy in that group, it is very, very difficult to succeed."

Asked whether Murray could win the Australian Open, Lendl replied: "That is obviously the goal. He does have a chance but I can't make any predictions."

Lendl was speaking at the launch of a tennis showdown event next year in which he will play against John McEnroe.