During one of the outright best main cards put together in the UFC's short history on Fox, we witnessed a true changing of the guard.
In the co-main event of the night, B.J. Penn was horribly outclassed by the young Rory MacDonald, visibly wilting in the second round of their fight as the massive Canadian landed knees, kicks, hooks and jabs seemingly at will.
Several Penn fans could only look on in horror as the UFC legend was beaten and bullied, at one point almost forcing referee Herb Dean to step in and stop the fight standing.
In three rounds of dominant aggression and showboating, MacDonald made it clear that he's a top welterweight, simultaneously edging Penn closer to irrelevance.
Things weren't much better for Mauricio Rua.
Although the former light heavyweight champion put in an incredibly gutsy effort against Alexander Gustafsson, "Shogun" simply didn't have enough power or speed to beat the Swede.
Still, Gustafsson didn't outclass Rua as badly as MacDonald did to Penn (and this author certainly doesn't think "The Mauler" has much for Jon Jones), but it was an impressive feat nonetheless.
Has the UFC's old guard lost it?
Seattle's KeyArena hosted one of the best fight cards this year at UFC on Fox 5, and when we look back at this night, we'll remember it as two things: the night that Penn's legacy died, and the night that Shogun Rua's legend started to fade away.
Both men have given the best of themselves to MMA fans over the years, so neither one has anything to be ashamed about.
Penn fought outside of his natural weight class against an opponent who dramatically outclassed him in guts, size and strength.
Rua's battle-worn body and crippled knees held up through three rounds of punishment against a man who Forrest Griffin famously declared no one wanted to fight.
Hopefully, Penn lives out a peaceful life of waning fame during his retirement years.
And when Shogun Rua hangs up his gloves for good, he should be remembered as one of the greatest light heavyweights in the sport's history, if not one of the all-time greats.
Sure, there's still plenty of old-timers sticking around like Anderson Silva, Frank Mir, Antonio Rodrigo Nogueira, Dan Henderson, Rich Franklin, Vitor Belfort and Wanderlei Silva. But Saturday night—and the future—belongs to the young guns of the sport.