Ivan Lendl threw up his version of an Iron Curtain when asked about the state of Andy Murray's mind and his game as the Scot switches his focus to the Australian Open in January.
Lendl steered Murray to the US Open crown in September, ending Britain's 76-year wait for a men's Grand Slam singles champion.
Many expect Murray to emulate his coach and win several more, but Lendl said it would not be easy.
"I never get into details of his game because it is not necessary for anyone other than Andy to know," Lendl said.
"The goal is to win in Melbourne. But tennis is difficult with (Novak) Djokovic, (Roger) Federer, (Rafa) Nadal and Andy all very good at the moment.
"Yes, he has a chance but I can't make any predictions."
A question on whether Murray could now dominate the sport was rifled straight back like a Lendl service return of old.
"I am not going to go there," he said, "The only way to answer that is to take one match at a time, one tournament at a time and see what happens."
Lendl, in Hong Kong to promote a global 'BNP Paribas Tennis Showdown' event in March in which he will play old nemesis John McEnroe, said it was impossible to compare eras.
"There are many eras in the game and there have been many good players at the same time," he said.
"You can look at the early 80s with (Jimmy) Connors and McEnroe, (Bjorn) Bjorg and myself, you can go back in to the 60s and 70s and there are many good players there."
One comparison he did make and the unflattering conclusion he reached was that he would not be able to live with Murray now. He smiled: "Andy would kill me."