Before his unanimous-decision win Saturday over the relatively unknown alphabet champion Jessie Vargas, Top Rank aired a highlight package of Manny Pacquiao's greatest hits.

For several minutes, boxing fans were treated to a walk down memory lane. Fists flew from all angles, lefts and rights blurring as they connected with an unlucky foe's head.

Pacquiao, in case you'd forgotten, was once among the most dynamic fighters in boxing history.

It was thrilling, but also a little bit sad. As his subsequent performance against Vargas showed, the past is firmly in the past. In front of a partisan crowd at the Thomas & Mack Center in Las Vegas, Pacquiao used his huge advantages in speed and craft to score point after point. But aside from a flash knockdown in the second round, the Pacquiao of old was nowhere to be seen.

Instead, fans were treated to an old Pacquiao, now a 37-year-old decision fighter. The whirling dervish who became a worldwide phenomenon is long gone. In his place stands a more cautious fighter wearing his face, a fighter who has gone almost seven years without a knockout.

Perhaps that's why the most exciting moment of the night didn't actually happen in the ring. It occurred when Floyd Mayweather Jr. found his seat on the floor, instantly creating thousands of tweets and no doubt dozens of think pieces just like this one.

Last May, Mayweather and Pacquiao rewrote the pay-per-view record book, generating in excess of four million buys and more than $400 million. The resulting fiasco and tepid fight left a sour taste in the world's mouth—but if even half of the customers can be convinced to buy a return bout, both men will once again be very, very happy.

While the crowd in the arena was enthused by the idea of a rematch, cheering loudly when announcer Stephen A. Smith mentioned Mayweather's name during the post-fight interview, Pacquiao himself was strangely noncommittal.

"I don't know," the new champion said. "Whoever the people want me to fight. I'm not picking anyone or choosing an opponent. Whoever my promoter gives to me, I'll fight."

It was a dodge worthy of Mayweather himself. It didn't expressly eliminate a rematch, but it didn't do anything to encourage further discussion.

Perhaps that's for the best.

A victory over Mayweather, who would turn 40 before a fight could possibly be made next year, is merely a win over another old man who didn't know how to say goodbye. It would be a contest between and for old men, a rematch of a bout that was already well past its expiration date the first time around.

Boxing is built on the bodies of its legends, the young replacing the old as idols and champions. Both Pacquiao and Mayweather were anointed kings at Oscar De La Hoya's expense. He, in turn, built his empire only after vanquishing the previous standard-bearer, Julio Cesar Chavez.

The next generation of stars were robbed of that opportunity by Pacquiao and Mayweather's sustained excellence. Even today, Manny was way too much for a good, but ordinary, young champion such as Vargas.

Only a great fighter can possibly hope to challenge Pacquiao and jot his own name into the history books. The fighters worthy of that task aren't on Instagram bragging about how much money they have and who they used to be. They are in the gym, honing their skill, and in the ring, dominating all comers.

Only a worthy foe will beat Pacquiao, even in this diminished form. Let them come forward while they still can. Bring on Keith Thurman. Give Errol Spence Jr. a chance or allow Terence Crawford to try his hand.

Let the future legends assume their rightful place on the mountaintop. And leave the past in the past—where it belongs.

Jonathan Snowden covers combat sports for Bleacher Report.