NEW YORK -- As much as the opening week of a baseball season always provides optimism, so too can it plant the seeds of doubt. For the first time this weekend, Major League teams tested themselves against other clubs trying their hardest to win. That can expose a flaw or two that might not have been visible amidst the backdrop of training camp.

So it was with the Mets, who absorbed a 14-1 thumping from the Braves on Sunday night at Citi Field to drop their first series of the season, two games to one.

• Box score

“Obviously, I don’t feel good about what I did today,” said starter Rick Porcello, who allowed seven runs in his Mets debut. “It was a terrible performance.”

Porcello was hardly the only culprit over the weekend, however, as the Braves exposed several issues in the Mets’ master plan. If they want to make a run at the National League East title, the Mets will need to figure out how to correct them.

Problem No. 1: The rotation has a hole

Porcello’s abbreviated start forced the Mets to turn early to Corey Oswalt, who had been a candidate to start Tuesday in place of injured right-hander Marcus Stroman. The Mets are calling Stroman and his torn left calf muscle a “week to week” proposition, meaning they will need not just a spot starter, but someone capable of taking the ball every five days for the foreseeable future.

What the Mets can do to fix it: The easiest solution would be to start either Erasmo Ramírez or David Peterson on Tuesday in Boston. Peterson in particular offers the promise of upside as the Mets’ 10th-ranked prospect.

A more creative solution would be one the Mets have been reticent to pursue for years: convert Seth Lugo back to a starting pitcher. Lugo has been outspoken about his desire to start, but the Mets believe he is more value as a multi-inning weapon out of the bullpen. Given Lugo’s success throughout his career, it’s not difficult to envision him as one of the five best starting pitchers on staff right now.

“Just as far as going out and starting, I’d do that anytime,” Lugo said. “I’m always ready.”

Following Sunday’s loss, manager Luis Rojas reiterated that the Mets are not considering Lugo as a starter. Perhaps in time that might change.

Problem No. 2: The team defense is suspect

This isn’t a new issue; to the contrary, the Mets have struggled defensively for years, regularly shifting players away from their natural positions with questionable results. That hasn’t changed under general manager Brodie Van Wagenen, who inherited a well below-average defensive team -- the Mets finished 30th in the Majors in Defensive Runs Saved in 2017 and 27th in ’18 -- and could only do so much to address it.

In the third inning of Sunday’s loss, J.D. Davis missed two balls over his shoulder in left field, posting route efficiencies of 82 percent and 69 percent on run-scoring doubles by Marcell Ozuna and Dansby Swanson, according to Statcast data. But like Porcello, he was far from the Mets’ only culprit. The usually sure-handed Jeff McNeil also made a key error, and the club struggled on defense throughout the weekend.

“We have a few guys in our rotation, like Rick today, that’s a guy that’s a contact guy,” Rojas said. “We need to have defense behind him.”

What the Mets can do to fix it: The Mets can’t improve their glove work without hurting their offense, which is another early point of concern after they were held to one run Sunday on Brandon Nimmo’s RBI double.

The Mets could replace Davis with Jake Marisnick, for example, but that would put a dent in their expected production. They could play rookie Andrés Giménez over 37-year-old Robinson Canó at second, but the Mets believe there is still thunder in Canó’s bat. They could move Davis to designated hitter and Yoenis Céspedes to left, but it remains unclear how capable Céspedes is of playing the field.

In his early days as manager, Rojas has proven aggressive in subbing both Davis and Canó out late in games for defensive purposes. That’s one way to mitigate the Mets’ issues. Realistically, it might be the only way.

Problem No. 3: The Mets may not have a reliable closer

Both Rojas and Edwin Díaz bemoaned that Díaz’s blown save Saturday was more due to Ozuna’s strong hitting than to anything Díaz did. But it’s impossible to evaluate Díaz without considering the backdrop of 2019, when he blew seven saves, lost seven games and posted a 5.59 ERA. If he’s that guy again, the bullpen is going to have issues.

What the Mets can do to fix it: Team officials have been quick to point out that four others in their bullpen -- Lugo, Jeurys Familia, Dellin Betances and Justin Wilson -- have closing experience. Familia in particular impressed during both Spring Training and Summer Camp, using his slimmed-down frame -- he lost more than 30 pounds over the offseason as a way to generate more balance and fluidity on the mound.

The Mets still seem committed to Díaz as their closer, but in a 60-game season, they can’t afford for his struggles to become a trend. Díaz could be a lone blown save away from losing his job -- though the Mets aren’t there yet.

“I’m not concerned,” Rojas said after Saturday’s loss. “We like how Díaz has been throwing the ball, what he’s shown repeatedly.”