Murray won Olympic singles gold at Wimbledon at London 2012, before claiming his maiden Grand Slam title with victory over Novak Djokovic in the US Open final in September.
The British Fed Cup captain believes Murray and Lendl have similar personalities and credits the Czech with helping her son develop an on-court “toughness”.
“He’s been a crucial factor in Andy’s improvement and success this year,” she told BBC Sport.
“The wonderful thing about Ivan is that he’s very similar in character to Andy, not least they have the same awful sense of humour!
“But seriously, he’s very driven, very dedicated and he absolutely has his eyes on the prize.
“He’s got a real sense of direction, a real toughness and he’s really helped Andy with the mental side of the game, about being able to reset if you suffer a disappointment, a bad call or a run of bad games.
“That’s allowed him to play his best tennis for much longer periods of time.”
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BIOGRAPHY: Cesc Fabregas