It had to happen, since finally it did: the mighty Swiss Guard of Roger Federer and Stan Wawrinka, owners of 23 singles Grand Slams between them, fell before the ruthless Slav steamroller personified by Daniil Medvedev and Grigor Dimitrov. Arthur Ashe Stadium, cathedral of the U.S. Open at Flushing Meadows, Queens, N.Y., was rocking and rolling last night as lean and hungry young men got what they came for.

The man whom his friend and compatriot calls Stanimal for his tenacity met his match after a fine run to the quarterfinals of the semi-centennial edition of the U.S. Open. He was unable to seize the initiative after the Russian prodigy, Daniil Medvedev, edged him in a first-set tiebreak and over the next two sets sustained an unshakable strategy of getting every shot back no matter how or where it came to his side of the court.

Medvedev reportedly suffered debilitating thigh cramps and had to adjust his tactics. His usual game involves covering the court like a center-fielder, getting his tall svelte frame in position well ahead of nearly every shot, reaching the others with his long reach and strong, quick swings. They are mysterious shots, very hard to read, because he crouches around them and hits on the rise and you never know the direction they are going until they are there. Yesterday he had to lob and change pace and make drop shots to prevent the mighty Stan Wawrinka from deploying his long bombs to the corners. When they are clicking they are among the most classy and aesthetically pleasing shots on the Tour, quite aside from being fast and hard and accurate. Wawrinka allowed after as how he never was able to get his rhythm going, letting Medvedev take charge of the points and set up his own opportunities to paint the lines with winners.

Throughout, the Medvedev plan was to get the most important point of the moment. The fact he and Wawrinka ended with nearly the same numbers in terms of points won was less an indication of a neck-to-neck race as it was of the Muscovite’s ruthless control. In this, as alert reader (and player) Frank Stieber has long pointed out, he has a game somewhat reminiscent of Nikolay Davydenko, who was in the top five in the late oughts and who played with relentless controlled fury.

Grigor Dimitrov, who is from Haskovo in southern Bulgaria and now lives in Monte Carlo, far from ex-girlfriend Maria Sharapova — this is TAS, not People magazine, but the fact is not irrelevant, because Grigor’s life and career often looks like sunshine falling on ice — had to battle through five nail-biting sets to overcome the man who has defined the sport in this century. Dimitrov has an explosive, good-natured, courteous, frankly happy personality that contrasts with the dark machine-like ruthlessness of many others on the Tour, including Daniil Medvedev and even the great Swiss maestro, to whom he often has been compared and who until last night had a 7-0 record against him.

For sure, Dimitrov’s style, not unlike that of France’s Gaël Monfils, could be set to an early Beach Boys song, exuberant, wildly athletic, funny, the stuff of showmen. Yet the popular nickname “Baby Federer,” usually associated with his footwork, big one-handed backhands, and ability to make seemingly magical shots, cuts both ways: Federer too, in his classic manner, is hugely athletic and can make the craziest shots, the famous ’tweeners, for example, that if he did not invent — but did he? — he certainly has made marvelous use of, as has Dimitrov.

You may want to know why so many Bulgars are named Dimitrov, but I say do not lose your focus. And indeed, it was his extraordinary ability to stay on point that allowed young Grigor to finally overcome his model and occasional practice partner — his teacher.

Sooner or later, the student takes down the master. They went four sets nearly point for point, and finally at the end of the fourth Dimitrov held on to the lead that allowed him to force a fifth set. Both men knew this was it, deuce to AD to deuce and repeat as first Federer sought the break he needed and Dimitrov insisted on the hold. After that, it was over, as Federer’s back allowed him only a perfunctory stand in the fifth set. Like a Swiss guard, he was faithful to the end, and he refused to quit, though retiring mid-match has become something of a fashion on the Tour.

It was surely a beautiful day (and night) for tennis, with the crowd finally taking Daniil Medvedev to its heart after booing him for upsetting old favorites. Maybe they glimpsed the big Russian soul under the killer look with which he sarcastically taunts his taunters. “Keep cheering [for the other guy],” he said in an earlier match, “I love it!” In the semis he meets his fellow Slav, who too, though he took down the most popular tennis champion of this generation, earned the fans’ admiration, fair and square.

So that’s it for now, though TAS sports must note for the record — since everyone must know it by now — that Serena Williams won her U.S. Open 100th match in Ashe Stadium (in between the men’s), knocking out China’s Wang Qiang in less than three quarters of an hour. This must be some sort of double record. Miss Williams is in great form, but it is likely her next match, against Odessa’s own Elina Svitolina (she moved to London), will test her more than the lovely Miss Wang who, though obviously a fine player, was totally out of it yesterday. Which is okay. It’s only tennis, but, like rock ’n’ roll, we love it.