WASHINGTON — It is hard to draw any conclusions after four games. That is merely 2.5 percent of the 162-game regular season, so please read the next sentence with that in mind. The Mets are one of the best teams in Major League Baseball.

On Sunday afternoon, they had a chance to become the first team in M.L.B. to reach four wins. On a home run by shortstop Francisco Lindor and a go-ahead single by outfielder Mark Canha, the Mets took a one-run lead over the Nationals in the fourth inning. But after some miscues on the mound by Mets relief pitchers and in the field by first baseman Pete Alonso, they lost, 4-2, to rebuilding Washington at Nationals Park for their first defeat of the season.

“It’s good to win the first series of the year, but dropping this one late kind of stinks, especially for me,” Alonso said. “I didn’t want to do that. I didn’t want to go out there and let anyone down, especially not anyone in the locker room. After not making the play there, I let the team down.”

Nationals 4, Mets 2 | Box Score | Play-by-Play

No one wants to lose, and defeats are inevitable during a six-month regular season. But in the season-opening series, there were encouraging signs for Mets fans that the team could contend for its first postseason spot since 2016.

First, the starting rotation has been stout. With the ace Jacob deGrom, a two-time National League Cy Young Award winner, possibly out for months with a right shoulder injury, the Mets will need the rest of the starting rotation to carry a heavier load. Through four games, the starting staff has a 1.59 E.R.A.

On opening day, Tylor Megill, making his 19th career start, filled in for deGrom and fired five scoreless innings. The next day, Max Scherzer made his Mets debut and produced a strong outing despite the remnants of a minor hamstring injury. On Saturday, Chris Bassitt, a 2021 All-Star acquired from the Oakland Athletics in a March trade, also made his Mets debut and threw six scoreless innings with eight strikeouts.

“I don’t care who you are. I’m coming after you,” Bassitt said then, referring to the Angels’ Shohei Ohtani and Mike Trout, who are former most valuable players and two of the best hitters in baseball. “I faced Ohtani a lot. I faced Trout a lot. I don’t care the name on the back of your jersey, I’m coming.”

The right-hander Carlos Carrasco, in his second season as a Met, followed suit on Sunday. After undergoing surgery to remove a bone fragment from his elbow last October and saying during spring training that it felt like he had a new elbow, Carrasco backed up his words. He allowed only one run over five and two-thirds innings and said afterward that a healthy elbow allowed him to use all of his pitches more frequently and effectively than before. His lone blemish: Nationals designated hitter Nelson Cruz’s first-inning blast, the 450th home run of his career.

“Carlos is in a different place right now than he’s been a while,” said Mets Manager Buck Showalter, adding later, “It was good to see him get off to a good start to the season because we could use him.”

Second, the Mets’ offense — and versatility in the field — has improved so far with the help of newcomers such as infielder Eduardo Escobar, and outfielders Starling Marte and Canha. Escobar is 3 for 11 and has played good defense at third base. Marte is 3 for 14 but has driven in four runs. And Canha, who collected three hits on Sunday, has played every outfield position and is 7 for 10.

One of the Mets’ weaknesses last year was their offense. They were 27th in runs scored per game (3.93), 20th in batting average (.239), 23rd in on-base plus slugging (.706) and 25th in home runs (176).

“The guys who we brought in have blended in real well,” Jeff McNeil, a second baseman and outfielder, said.

Bassitt said people should expect talent with a large payroll (the Mets’ franchise-record mark of $286 million trails only the Los Angeles Dodgers for the highest in M.L.B.). But he praised the Mets’ mentality, particularly at the plate.

“There’s a lot of guys, a lot of teams, that it’s all or nothing,” he said. “This team is not like that. We might be able to hit some homers. We’re just going to grind you until you break. And that’s the mentality we’ve been preaching since Day 1. We have a pitching staff to hold it down until that happens.”

It didn’t happen for the Mets on Sunday. Erick Fedde, the Nationals’ starting pitcher, surrendered two runs over five innings, and then four relievers combined to allow just two hits.

And in the eighth inning, the Mets’ pitching and defense faltered. Because a labor dispute led to an abbreviated spring training, Showalter has been careful with his bullpen early. So instead of the team’s best relief pitchers protecting a 2-1 lead, he turned to the left-hander Chasen Shreve and the right-hander Trevor Williams, who combined to allow three runs. (The Mets’ closer, Edwin Diaz, is on the bereavement list after the death of his grandfather.)

The Nationals tied the score when they pulled off a safety squeeze, with the rookie Lucius Fox bunting and Dee Strange-Gordon sliding home safely. Alonso said he tried his best on a difficult play. Showalter pointed to the cold weather but said Strange-Gordon would have probably been out if Alonso had gotten the ball out of his glove more cleanly to throw home after fielding the bunt.

Two plays later, Alonso’s wide throw to second base prevented the Mets from turning an inning-ending double play. Two batters after that, Cruz gave the Nationals a 4-2 lead with a two-run single.

Up next for the Mets are three games against the Philadelphia Phillies, one of the division rivals expected to battle them and Atlanta, the reigning World Series champion, for the top spot in the N.L. East.

“This team is really good — the position players, the starting pitchers, everyone,” Carrasco said on Sunday. “So we showed out there we’re really good. The important thing is to stay healthy and keep playing hard.”