ST. ANDREWS, Scotland — The bespectacled, white-haired journalist from The Surrey Advertiser, on hand to chronicle his 37th consecutive British Open, cocked his head and asked Jordan Spieth a question that cut through the crosswinds during the tournament as deftly as did one of Spieth’s crisp iron shots on the Old Course:

When did golf become so youthful?

Down the stretch of Monday’s finale, the usual cast of leading men was nowhere to be seen. Tiger Woods, a 14-time major winner, failed to make the cut. Phil Mickelson, who has not won since the 2013 British Open, teed off early and put together a quiet three-under-par 69 to finish tied for 20th, eight strokes back. Rory McIlroy, the world No. 1 and the event’s defending champion, never made it to the first tee. Sidelined with a badly sprained ankle, McIlroy was out of sight, out of mind.

In five news conferences with the print media over six days, the second-ranked Spieth was asked 64 questions, and the only time McIlroy’s name came up was when Spieth casually mentioned him in a list of players whose power off the tee he could never hope to match.

Last summer, McIlroy was golf’s transcendent figure, with victories in the British Open and the P.G.A. Championship leaving him one Masters title from a career Grand Slam. Having taken the mantle from Woods, though, McIlroy, now 26, found Spieth, an avid basketball fan, battling him for it as if it were a jump ball. Spieth could have supplanted McIlroy at No. 1 with a victory Monday. His tie for fourth only delayed what appears inevitable.

Once hailed as golf’s young gun, McIlroy must feel, suddenly, as if 26 is the new 36. Spieth, who turns 22 next week, is blazing a trail for the millennials. On Monday he battled rain, wind, a few golf ghosts, his putter and the Road Hole and came within a holed chip or a made 6-footer of joining Zach Johnson, Marc Leishman and Louis Oosthuizen in a playoff. Spieth’s play in the first three majors disinterred sepia-toned memories of Bobby Jones, who opened his successful Grand Slam bid in 1930 with a victory in the British Amateur at the Old Course.