John McEnroe’s and Ivan Lendl were great players of the 1980s. McEnroe was the #1 from 1981-94 and Ivan Lendl was #1 during 1985-87, 1989.
In 1982, while McEnroe was on a winning streak with other players, he was facing a very stiff competition from Lendl. McEnroe writes in his autobiography:
Lendl cleaned my clock once more, beating me for the seventh straight time… I couldn’t even come close to breaking his serve at that point.
McEnroe mention in his book, how a phone call from Don Budge (the last American, until then, to have won the Grand Slam, in 1938) gave him a crucial insight on how to beat Lendl:
“You’ve got to attack him right up the middle. Stop giving him the angles—he’s killing you on those angles.”
It was a simple advice, but the more McEnroe thought about it, the more sense it made to him.
Lendl was quite athletic. He could run all day. He liked being stretched out in the corners. Hence, he could access McEnroe’s angled shots and return powerful ground strokes at various angles (as shown by red lines in the figure below)
But, if McEnroe kept his shots in the middle of the court, Lendl would not be able to hit angled ground-strokes. He would be forced to lob or hit to McEnroe’s volley—which were McEnroe’s strengths (McEnroe was basically a serve-and volley player)!
McEnroe followed this insight–and ended up winning his next 9 matches against Lendl!1