Ivan Lendl has denied money was behind his surprise decision to coach Andy Murray after fellow great Jim Courier suggested there were "mercenary" reasons for the move, a report said on Tuesday.
The eight-time grand slam winner has returned to full-time tennis after playing for the last time in 1994 and has been ever-present in Murray's box during the Australian Open's early rounds.
But he was hit by a broadside from Courier, a commentator for Australian TV, who said the Czech had financial incentives for his move.
"There is a reason and it is a little bit more mercenary," Courier told Channel Seven, according to Britain's Daily Telegraph.
"He hasn't been allowed to make any money from tennis for the past 15 years because he cashed in disability insurance. That is the reason Ivan is back playing. There are all sorts of complexities there."
But Lendl called Courier's comments "ridiculous", according to the Telegraph.
"That's ridiculous," he was quoted as saying. "Jim shouldn't be saying stuff like that. First of all, it's wrong and he doesn't have the proper information. End of story."
Both Lendl and Murray have been positive about their partnership, which only began at the start of this year.
"When you just get that little bit of extra help from someone that's been there and done it many, many times, it helps," Murray said on Monday, after reaching the quarter-finals.