The day pitchers and catchers report to spring training, as the Washington Nationals did here Thursday, is a favorite on the baseball calendar. Nobody has to do anything except say, “I’m here.” Yet almost every player is so eager to start the new season, so sick of winter, so jacked with hope, that the parking lot is filled by 8 a.m. Some have been here a week.

On Saturday, with sun and 71 degrees forecast, the Nats will hit the field for an actual practice. But for this one day, big league ball is like taking attendance in kindergarten, except the class earns $152 million. Gio Gonzalez throws his arms around General Manager Mike Rizzo’s shoulders and says, “What’s up, Rizzy?” But a different pitcher tells Rizzo he couldn’t bear to watch the World Series because the Giants, who knocked out the Nats, were in it. “That was a tough way to end,” Rizzo says soberly.

Catcher Wilson Ramos has his brother sit at his locker as teammates watch to see whether a reporter will interview the wrong Ramos. Yes, one does. Danny Espinosa shows up with a huge Fu Manchu that covers almost half his face. “He hopes the pitchers won’t recognize him,” someone quips.

Pitching coach Steve McCatty says, “I was on the phone with the Tigers’ pitching coach, Jeff Jones. He said, ‘You got Doug Fister from me last year, now Max Scherzer. Who else do you want?’ ”

A cloudless, sun-soaked day awaited the Nats, appropriate for a team whose pitching prospects are almost cloudless. You would call it blue-sky perfect except for the annoying necessity to play the season.

The Post Sports Live panel discusses Drew Storen's struggles in the closer role and other potential issues facing the Nationals as they head into spring training. (Post Sports Live/The Washington Post)

Somewhere, McCatty is waving his arms, so let him make his point: “When you hear this stuff about how good you are, be careful. Don’t believe it. That’s when you get your butt kicked.” Cat knows firsthand. In May of 1980, the A’s were in first place with a five-man rotation, including McCatty, on pace for 100 complete games. “Some people said we might have five 20-game winners,” McCatty said. Reality arrived. The A’s threw 94 complete games but had only 83 wins.

So even on Day 1, baseball’s love of the colossal comeuppance must be acknowledged. But that caution misses the larger point. The Nats have assembled the best rotation — albeit on paper — in the history of Washington’s 81 MLB seasons back to 1901. Few teams have even approximated it. Fans at Nationals Park may have a unique experience all season. In response to the inevitable, “Who’s pitching tonight?” the answer may be the same: the ace.

“This rotation, it’s pretty unbelievable. You’ve got flame throwers and your lefty. Fister, when he threw 90 [mph] against us in Toronto, my teammates would say it looked like 97,” said free agent reliever Casey Janssen, who’s tabbed for Tyler Clippard’s setup job. “Before [a series] you could ask the other team which three they wanted to face, and it wouldn’t make any difference. Any three would be just as good.”

Scherzer, the 2013 AL Cy Young Award winner, fanned 252 men last year, even more than Stephen Strasburg, who tied for the NL lead (242). Gonzalez has won 21 games and Jordan Zimmermann 19. Fister was fourth in the NL in ERA. There are a zillion such flattering stats. But here’s the knockout: In the past three years, the Nats have five of the top 18 pitchers in MLB by ERA: Zimmermann (fifth at 2.96), Strasburg (12th), Fister (14th), Scherzer (16th) and Gonzalez (18th). No other team has more than two. And the Nats’ sixth starter, Tanner Roark, had a 2.85 ERA last year.

For analytics lovers (me), the Nats also have five of the top 24 pitchers by WAR (wins above replacement) over the past three years. And Roark actually led the Nats in pitching WAR (5.1) last year.

If the Nats need further help, Fister says Scherzer is a student of the game who helps other pitchers and “has a good personality that has the capacity to glue people together. . . . He can be a jokester. But [in games] he battles.”

There may never be a day when the Nats’ pitching looks quite as superb as it does right now, before the first injury or worries that a back end of the bullpen with Aaron Barrett, Janssen and Drew Storen might merely be good but not exceptional.

Nonetheless, Rizzo was stumped by only one question all day: What is your biggest worry? He was silent for 30 seconds. “There are questions on every team but not a lot of major concerns. Don’t wanna sound cocky,” Rizzo said. He then ran through issues such as improving bench production, adapting Ryan Zimmerman, Yunel Escobar and Jayson Werth to new positions (first base, second base and left field ), as well as the presence of only two everyday lefty bats.

“Those are all true,” he said of the potential flaws, “but all manageable. . . . Remember, five years ago we said, ‘Without a rotation, nothing is possible. With a rotation, everything is possible.’ ”

Say hello to “everything”: a rotation with a 15-game winner in reserve. Take a good look. One might get traded. Others could get hurt. And nobody thinks all six will be back in 2016. What Washington is seeing is unique in its baseball history — and just one day old. Perfect in theory and perishable for certain. Appreciate it while it lasts.

For more by Thomas Boswell, visit washingtonpost.com/boswell.