On opening day, baseball happened to the Washington Nationals — all of it.

Thrilling comebacks, clutch hits and scary moments of potential injury to stars all arrived in one big crash at Citi Field. Even the Nats’ eventual victory was left with a worrisome “to be continued” hanging over it. On Tuesday, catcher Wilson Ramos’s injured left hand will be examined. Save something for the other 161 games, can we?

In a 10-inning, 9-7 win over the Mets, the Nats witnessed the debut of Manager Matt Williams who, it seemed, was required to present his entire baseball doctoral thesis in one 3-hour 47-minute exam.

“I have a stomachache,” Williams said afterward, honest but grinning.

The new manager pinch-hit for a pinch hitter, double-switched his face of the franchise out of the game, challenged a call, used Danny Espinosa as a pinch hitter in a desperate down-to-the-last-out situation and put reliever Aaron Barrett into a 5-5 game in the bottom of the ninth in the kid’s major league debut. And almost all of it went very right, none of it wrong.

Anthony Rendon, who stayed in the game at third base when Ryan Zimmerman left, hit a three-run homer in the 10th and finished with four RBI. “Some guys just have it. He has it,” Denard Span said.

Espinosa, down to the game’s last strike, drew an eight-pitch walk to keep the game alive so that Span, who had already tied the game once with a bases-loaded walk, could knot it again at 5 with an RBI double.

Barrett, his name misspelled “Bartlett” on the Mets’ scorecard, had a perfect inning with two strikeouts and ended up the winning pitcher.

“Surreal,” he said, an understatement.

That was the small stuff, just the warmup. The more important long-term issues are, to varying degrees, undetermined. Hold your breath.

Before the game, Williams named Ramos his cleanup man — an opening day surprise — while batting Zimmerman No. 2 and Bryce Harper No. 5. Before the seventh-inning stretch, opening day had its own ugly surprise for the Nats as Williams took his catcher out of the game for X-rays of his left hand.

“It’s negative on the initial X-ray. That’s good,” Williams said. “But we don’t know yet.”

By the second inning, Williams also raced to second base to find out whether Harper had knocked himself out, broken his ankle or destroyed himself in some new imaginative way with a late, awkward slide to break up a double play. After Harper eventually rose from the dirt, Williams had to decide within minutes whether to let the rambunctious 21-year-old who always says “I’m okay” stay in the game.

Harper remained in left field and later lashed a single off the very infielder, Eric Young Jr., whose shin had laid him low. After the game, Harper said he had passed two concussion protocol tests — one during the game, one afterward.

“I feel all right,” he said. “Young blew me up a little bit. . . . I’ve got a pretty bad headache. . . . No ‘hazy’ or ‘dizzy’ but my head hurts pretty bad.

“I didn’t see stars, and I have seen stars before.”

The Nats had nothing but stars. “That was such an amazing team win. I could name everyone on the team,” said Barrett, only slightly exaggerating.

If the ebullient Barrett is close to being as good as he’s seemed this spring, the Nats have found another bullpen arm. “Oh, he’s got a breaking ball, you think?” said Drew Storen, who had an impressive slider-filled inning of his own.

“Last year, when we got down early, sometimes we folded,” Span said of a Nats team that didn’t have a single comeback comparable to this until June of last season. “This year, everybody just came in with a little different attitude.”

Seasons are organic creations, not foregone conclusions based on past performance, predictions or statistics. One game is the tiniest sample but can be indicative. Stephen Strasburg, sometimes rattled when a game started badly for him, ignored four Mets runs within the first 10 batters as well as a 44-degree game-time temperature with strong, cold winds. He settled in like a veteran, found out what he had — command of all of his off-speed pitches, including his new slider — rather than worry about what he lacked, his best fastball.

“I settled down and kept us close,” said Strasburg, who left a 4-4 game with 10 strikeouts in six innings.

If any player symbolized the Nats’ failures and frustrations last year, it was Espinosa, who whiffed his way back to the minors. Last year, with the Nats down to their last out, then last strike, he might have swung for the fences and fanned. This time, he fought off four foul balls, including a rocket down the first-base line, and took four borderline pitches for balls to draw a walk that moved the tying run into scoring position for Span.

“I got my name called,” Espinosa said. “I was ready.”

Like the rest of the Nats, however, he had Ramos in his thoughts. Even the biggest men have so many tiny bones in their hands. “It’s unfortunate. I really feel for him,” Espinosa said. “We all hope for a quick return.”

Baseball seasons are often about swallowing what appears indigestible. “This game is pretty ruthless sometimes,” Storen said. “It’s been especially tough on [Ramos]. It’s not an accident that he’s hitting in the middle of our order.”

If a team ever wanted a day for multiple contributors and successful debuts it was the Nats as they fretted out Ramos. “You feel for him. He’s been through a bunch. Just bad luck,” Zimmerman said.

Several veteran players pointed out that, as with Doug Fister’s current stint on the disabled list, they intend to play through whatever confronts them. That’s part of opening day confidence. But the Nats are also buoyed that one of their last offseason additions was an upgrade at backup catcher — Jose Lobaton. Last season, he led a 92-win Tampa Bay team in innings caught. On Monday, he had a hit and scored in the Nats’ four-run, game-winning rally in the 10th inning.

“When a team wins as much as the Rays did last year with Lobaton playing in 100 games, he’s got to be doing a lot of things right,” Zimmerman said.

In 2012, the Nats had lots of major injuries, many early, but used them to unearth new key players who made the team more confident in a season when comeback victories bred off themselves. Last season, bad luck was just bad luck. Which kind of season is this? On his debut day, let Williams frame it his way. “We think games like this are in our DNA as a team,” he said. “We never give up. We never give in.”

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