Andy Murray achieved five break points in the fifth game of the first set against Jo-Wilfried Tsonga, including a remarkable clutch forehand on a shot that no one reasonably would have expected him to retrieve. Murray’s extreme physical speed combined with what surely are some of the quickest wits among top ten tennis players render him unpredictable. When he is hot, it is impossible to keep up with the variety he can put into play, ranging from perhaps the best return of serve in the game today to lightning reflexes at the net. From the baseline he can control the point with his consistent two handed backhand and a seemingly effortless ability to suddenly quicken the pace of play.

It was by virtue of what he called his “hot game” that Ivan Lendl became the dominant player of the mid to late 1980s, but, if memory serves, his game was not quite as varied as Murray’s. Like Murray, whose coach he became a couple years ago, he could play a powerful and consistent baseline game, and was fast enough to catch most of what was sent to his corners. He did not have quite so tactical a serve, however, and he did not have a net game, at least not the net game that contributed to Murray’s victory at Wimbledon last year, the first British man to conquer the trophy at the All-England Club since the legendary Fred Perry’s second consecutive win there in 1936. Orthodoxy has it that you cannot win on grass without a net game and here orthodoxy is right, as it most usually is in most things. Lendl won everywhere else.

Murray could not win anywhere when he asked Lendl to coach him. A perennial runner-up, he suffered his frustration in dignity, though with occasional bodily and verbal outbursts of anger on the court, directed at himself.

Lendl, famous for his poker-faced stoicism, may have recognized something in that determination. He shared with Murray the experience of reaching several finals at grand slam tournaments before winning one. Maybe he wondered, in his retirement, whether it was mental or physical, the key to the crown. In some athletes the answer is obvious, but in others, such as Lendl and Murray, it remains elusive.

Against Tsonga in the Sony Masters fourth round at Miami’s Crandon Park, the question remains open. The weight of the evidence suggests a qualitative mental change over the past two seasons, during which Murray broke through not only at last year’s Wimbledon but at the London Olympics and the U.S. Open in 2012. Murray’s speed and strength were on full display, with masterful net play worthy of the great grass court days of the sport. Tsonga too is an excellent, aggressive net man, and his own play in the forecourt made this one of the most exciting matches in the tournament so far. What was especially remarkable, however, was Murray’s cool consistency. To be sure, the change from the pre-Lendl years has been apparent for some time and it was accentuated here by Tsonga’s own notorious tendency to flub in the clutch. The lopsided score belies the fierceness of the contest between the two, but it also underscores the huge change Lendl has made in Murray’s game.

You can also argue, of course, that change happens anyway. To that you answer that it just so happens that this cannot be proven, whereas it is known that Lendl was there when the change took place. Lendl quit coaching, at least for now, just prior to Miami, where Murray is the defending champion. A transcript of their last meeting, at a local restaurant, has not been released, but it is clear they are on the best of terms. It is not unreasonable to guess they agreed that, apart from Lendl’s commitments, to family, high-level golf, champions’ circuit tennis, there was agreement on the risk of staying on a plateau. A teacher must know when these moments occur, when even greater learning depends on telling his student to move on.

One champ whom you would not suspect of needing help on the mental side is Roger Federer, who is called the master for a reason. He shows emotion, reveling in victory and unhappy (though not bitter) when he loses, but he does not show temper. He opposed the idea of hawk-eye backed challenges, has not spoken out in favor of a “fifth grand slam,” as some players and commentators have. He is, in short, a classicist who knows the value of tradition and has outstanding mental as well as physical reserves.

Still, the choice of Stefan Edberg in a role somewhat comparable to the one Lendl played for Murray, may have more to do with confidence than you would think (or dare suggest). Federer’s game this year has been almost flawless. Even in his loss in the final against Novak Djokovic at Indian Wells a few weeks ago, it was clear the match was a contest between two champions in complete control of their games, and its conclusion was unpredictable until the third set tiebreak, when the mighty Serb pulled away.

Last year there were known physical problems, notably a back ailment that was clearly impairing Federer’s play. There was also a certain visible weariness. Many commentators speculated Federer’s age was catching up with him — he is 33 this summer.

To which the obvious answer is the history, or biography if you prefer, of any number of great champions. However, Edberg had, in his time, a classic serve and volley style that Federer admired growing up and that more than any other player of his rank in his generation he has emulated. Edberg, perhaps, encouraged Federer to trust the fundamentals of his game. The real test will come after the coming clay court season, on grass and then during the campaign leading up to the U.S. Open. But the results so far reinforce the Lendl-Murray experiment, with a classical conclusion: know yourself.