In the end, it was Murray who outlasted his Argentine opponent 7-5, 4-6, 6-2, 7-5 to strike gold for the second straight Olympics.
Here are five takeaways from a battle that won't exit our memory bank anytime soon.
1. Murray becomes the first player to win two golds in the Olympics
Certainly, tennis doesn't have the Olympic history of some other sports, but after a lengthy hiatus, it made its return as a full medal event in 1988. Since then, no player had won two gold medals, never mind consecutive Olympic championships. Until now, that is. Four years ago, Murray thrilled his home fans in London by taking Roger Federer out in the finale, and on Sunday in Rio, he squeezed by del Potro in an electric gold-medal match.
2. Murray thrives playing for his country
True, Murray had a long history of falling short on the grand stage. He started his career by becoming the second player in the Open era to drop his first four Grand Slam finals. (The other was Murray's current coach, Ivan Lendl.) To date, Murray has lost all five of his Australian Open championship matches. But don't discount the motivation Murray has when it comes to playing for his country. In 2013, he captured Wimbledon and became the first British player since Fred Perry 77 years earlier to win the title. Last season, he led his British team to its first Davis Cup championship since 1936. Now, a month after snaring the Wimbledon title for a second time, Murray -- Great Britain's flag-bearer last week -- owns two golds.
3. Del Potro is no ordinary No. 141
The 6-foot-6 Argentine has experienced setbacks no top-tier tennis player should endure. He has undergone four wrist surgeries and missed more than two years' worth of action. All this came after he stirred the New York crowd with a punishing, five-set win over Federer in the 2009 US Open final. Since then, del Potro has spent most of his time either sidelined or toiling on the comeback trail to find a modicum of the player he once was. But make no mistake: When the US Open rolls around in a couple weeks, no seeded player is going to want to see him in the opening round. Just ask Novak Djokovic.
4. A forehand, a serve and a heart
Since he came back from his wrist surgeries, del Potro's backhand has more or less been relegated to a slice that doesn't penetrate through the court in the same manner as a traditional, two-handed shot. Thus, he relies on a colossal forehand and a serve equally as heavy to get through matches. But del Potro's bread and butter these days might be the size of his heart. There were many times against Rafael Nadal in the Rio semifinals and again in Sunday's championship match when del Potro appeared drained, both mentally and physically. But the raucous support of the South American crowd wouldn't let him give in. Del Potro broke into tears of happiness many times the past week, including after his massive upset of Djokovic and his shocking win over Nadal on Saturday.
5. Protecting the serve proved difficult
Of all the noteworthy stats in this 4-hour, 2-minute classic, perhaps the one that stood out most was the breaks of serve. In total, there were 15 -- nine from Murray and six by del Potro. At one point, ranging from the end of the third set to the beginning of the fourth, the players exchanged five straight breaks. Later, with del Potro up 5-4 and serving to send the match to a decisive fifth set, he was broken once again. In the next game, Murray was down 15-40 but strung together four straight points to take a 6-5 lead. Finally, if not fittingly, Murray broke del Potro one last time to grab his latest gold medal.