DOWN the corridors of Melbourne Park you find them, this army of Yodas in shorts, walking behind players like a band of tennis whisperers.
Later they sit unmoving in the players' box, their life expectancy unknown, unable to play a match yet hoping their one idea can affect its outcome.
Welcome to the world of the coach, or as Stefan Edberg, Roger Federer's cornerman, told me and a fellow writer yesterday: "It's more difficult to watch than play."
On court 16 yesterday, Edberg and Severin Luthi, the Swiss Davis Cup captain who doubles as Federer's second coach, watch their player polish his return of serve.
It is unkindly hot but Federer wears no hat and merely produces his own brilliant heat. Later, the three men converge. Talking footwork? Or where to dine?
Tennis remains madly enamoured with the idea of star coaches and yet also two coaches. Novak Djokovic has Marian Vajda and Boris Becker.
Even Rafael Nadal has Francisco Roig as an understudy to his regular coach, who is splendidly unusual for he has no playing CV. Uncle Toni has always been a man apart.
Andy Murray, agile mind hidden behind dour face, was the unlikely trendsetter. First, in a brilliant experiment, he hired Ivan Lendl, who had never coached before. Then, to the spluttering of occasional chauvinists, he took on a woman, Amelie Mauresmo.
Men have always coached women and the reverse seems logical to Ivan Ljubicic, once world No. 3 and now one of Milos Raonic's coaches.
As he said: "It's the same sport. I don't see any issues there. (The men's game) is faster, but the coach has to tell the player what to do, not do it for him."