Then you start thinking about all he did in the postseason -- you know, when it really counts.
And that's when it hits you: 600 saves isn't even Mo's most impressive career accomplishment.
Lost in the discussion of the new benchmark Rivera just reached is the fact he already has an astonishing 42 postseason saves under his belt -- 24 more than any other man in history -- and doesn't look to be done yet.
With so many young, live arms getting full-time opportunities to close so early in their careers, there's a chance (albeit a very slight one) that one day somebody will top Rivera for the all-time regular-season saves record.
But will anybody ever come close to saving 40-plus games in the postseason?
Can anybody approach the most tense of playoff moments, in the most demanding city in the country, and deliver with such calm and such precision -- over and over and over again?
En route to five World Series championships, Rivera has appeared in 94 career postseason games -- 39 more than any man in history -- and has notched an all-time low 0.71 ERA.
Nos. 2 through 5 on that ERA list -- Harry Brecheen, Babe Ruth, Sherry Smith and Sandy Koufax, respectively -- each pitched in fewer than 60 playoff frames. Rivera posted his mark through 139 2/3 innings. In that span, he gave up just 11 earned runs -- or one run every 12 2/3 innings -- struck out 109 batters, walk 21 and put up a 0.766 WHIP.
Most impressive of all?
"Really how he's kept his edge," said former Yankees manager Joe Torre, who currently serves as Major League Baseball's executive vice president of baseball operations. "I think that's probably more impressive than anything else is how it continues to be very important to him and necessary to do what he does."
Of course, Rivera's postseasons weren't always perfect.
There was the eighth-inning, game-tying homer he served up to Indians catcher Sandy Alomar Jr. in Game 4 of the 1997 American League Division Series.
There was Game 7 of the 2001 World Series, when Rivera was spotted a one-run lead in the bottom of the ninth and gave it up.
And there was the 2004 postseason when he blew three saves.
But the sight of Rivera not being able to close out a game when the stakes are high is about as rare as double rainbows, blue moons and shooting stars. More common are the clutch saves he gets that you really don't think twice about -- because they have become as routine as ceremonial first pitches, Kiss Cams and the seventh-inning stretch.
"He's certainly able to focus on the moment, focus on what he needs to do," Hall of Famer and Yankees legend Reggie Jackson said. "Nothing really gets in the way of it. When he winds up with a loss or blows a save, you can't say it doesn't bother him, but you can certainly say he's able to channel it properly. He's able to put it in its place and give it perspective and move on."
From 1998-2000 -- against the Padres, Braves and Mets, respectively -- Rivera recorded the final out in a Yankees championship, notching Most Valuable Player honors for the '99 World Series along the way. He hurled 34 1/3 consecutive scoreless innings during that time, posted a 0.33 ERA in his first 55 playoff frames and converted 23 consecutive postseason saves from 1998-2001. All are records.
Then came perhaps his most impressive postseason performance, when in Game 7 of the 2003 AL Championship Series against Boston, Rivera entered the game in a 5-5 tie and pitched three scoreless innings, setting it up for Aaron Boone's walk-off homer en route to being named the ALCS MVP.
In those 2003 playoffs -- which ended in a World Series defeat to the Marlins -- Rivera recorded five saves of six outs or more. Now, he has the record with 14 such saves in the playoffs.
"As far as Most Valuable Player in those World Series," Torre said of his four championship teams, "he certainly shouldn't take a backseat to anybody."
For 15 years now, Rivera -- with his unhittable cutter, inexplicable calm and signature Metallica entrance music -- has been closing out games for baseball's most pristine franchise, bringing uncommon stability to a position with perhaps the most turnover. That was evident two years ago, when a 39-year-old Rivera recorded the final out in Game 6 of the 2009 World Series against the Phillies.
That season, Rivera was one of just three Yankees -- along with Andy Pettitte and Derek Jeter -- to be around for all five titles. And he was one of just five closers from 1997 still consistently closing out games 11 years later. The other four -- Todd Jones, Troy Percival, Trevor Hoffman and Billy Wagner were the others -- are gone now, and only Rivera remains.
That type of stability can be chalked up to Rivera's dedication and talent, sure. But perhaps more than anything, it's due to the fact his arm only needs to worry about that one nearly unhittable pitch.
"It's a double-edged sword with him, because you can say, 'How does he get away with one pitch?'" former teammate, fellow reliever and current MLB.com analyst Jeff Nelson said. "Well, the pitch is so dominant, and I think in that case, that's all he has to worry about is one pitch. You look at other closers, how many pitches do they have? Two and three. ... His motion is so fluid, he repeats the same delivery all the time, his release point, probably 95 to 97 percent of the time, is the same, and he has such great control of that one pitch."
Because of that, and because of the unhuman character traits that make him so determined, so focused and so emotionally stable, Rivera is the greatest ninth-inning man in baseball history. That much we know.
But is it possible that the greatest postseason pitcher of all time is a closer?
Very much so, indeed.
Alden Gonzalez is a reporter for MLB.com. Read his columns and his blog, listen to his podcast and follow him on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.