Chuck Stephens in The Criterion Collection:
…alongside the seven blade runners of Akira Kurosawa’s sword-toting supergroup there might have strode an extra warrior—an “eighth samurai.”
In fact, the existence of a supernumerary slice-artist among those Seven Samurai has been verifiable all along, and sharp-eyed cineastes will have long since spotted his inaugural if momentary membership in that Kurosawa-gumi, just as you can today—by scanning and rescanning the frames between the film’s ten-minute-sixteen- and ten-minute-nineteen-second marks. The fleetingly glimpsed swordsman who saunters through those scant few frames of screen time has no bearing on that 1954 classic’s surrounding narrative, and if you blinked through those three seconds, his absence would remain unfelt—he is but one stubbly bearded mercenary among the many potential warriors-for-hire that the film’s desperate rice farmers observe striding through the city, his only attribute an attitude of indifference, another replacement killer, cameo’ed and left unnamed. But for Tatsuya Nakadai—then a contract player at Shochiku Studios and not yet twenty-three years old—those flash-frames in the spotlight would prove three of the most decisive seconds in front of a camera an actor ever spent.
More here. [Thanks to David Maier.]