NEW YORK -- Having just walked three of the four batters he faced in the seventh inning Tuesday, Mets reliever Jake Diekman returned to the home dugout, received a few conciliatory pats on the shoulder, then fired his glove at the wall. Diekman stalked the length of the Citi Field dugout, kicking at the ground. From there, he descended into the clubhouse tunnel.

Diekman’s trio of walks was not the reason why the Mets dropped a 4-0 contest to the Phillies, who swept the first half of a four-game, home-and-home series on the strength of their exceedingly sharp starter, Aaron Nola. But they were thematic of the year to date. Through nearly seven weeks of season, Mets pitchers have issued 187 free passes, which leads the league. They have walked 11.8% of the batters they’ve faced, which also leads the Majors.

Those walks have led to a litany of issues, including a heavily taxed bullpen and an inability to rein in the opposing running game.

Mostly, though, they have led to runs.

“That’s a good question,” manager Carlos Mendoza said when asked about the walks. “I know [pitching coach Jeremy Hefner] is working really hard. A lot of our group is working really hard. It’s just one of those that since Day 1, we’ve been addressing the pitching: ‘Stay on the attack, get strike one, get two strikes.’ And we haven’t been able to do that.”

Why the Mets are walking so many batters isn’t entirely clear. Much is due to a change in personnel; over the offseason, president of baseball operations David Stearns collected a small army of pitchers with wipeout stuff but known control issues, including three who appeared in Tuesday’s loss: Diekman, Yohan Ramírez and Jorge López. Starting pitching acquisitions Adrian Houser, Sean Manaea and Luis Severino all rank in the Top 25 in MLB walk rate as well (among pitchers who have thrown at least 30 innings).

So do incumbents Jose Quintana and José Buttó, the latter of whom started Tuesday’s game. Buttó exemplifies the trend’s frustrating nature. As a regular rotation member, he has held opposing hitters to a .168 average, which makes him statistically harder to hit than Nola, Zack Wheeler, and all but six qualified Major League pitchers. But Buttó has just one win in seven starts, largely because of his control issues.

Tuesday, after throwing two scoreless innings, Buttó walked the bases loaded with two outs in the third, hit Alec Bohm with a pitch to force in a run, then walked Brandon Marsh to send in another. He finished with four walks in five innings. Over his last 26 innings, he has issued 17 free passes and hit three batters.

“I don’t know,” Buttó replied when asked about the source of the problem. “I just go there to do my thing, and that happened. I try to be better in my bullpens and everything, and that happened. The only thing I can do is keep working and improving.”

Diekman pointed to a series of pitches that he uncharacteristically “yanked” against left-handed hitters Kyle Schwarber and Bryson Stott in the seventh. Typically when he’s fighting his control, Diekman said, his misses to lefties are up and inside. Tuesday’s results suggested that his mechanics were out of whack. He planned to watch 3D skeleton video to see how his body was moving compared to earlier this month.

“I’ve never yanked that many balls in a row,” Diekman said. “I don’t know.”

Things haven’t always been this way. As recently as 2022, the Mets ranked in the top five in MLB walk rate. But most of the veterans who contributed to such excellent collective control, including Max Scherzer, Jacob deGrom, Carlos Carrasco and Chris Bassitt, have departed. Two relievers from that team, Adam Ottavino and Edwin Díaz, have since seen modest increases in their walk rates. But much of the trouble can be traced to pitchers who weren’t on the roster in ’22.

Particularly in a small sample size, walk rates will fluctuate season to season. Still, Mets pitchers have now thrown 370 innings, with a walk rate about 70 percent higher than it was two years ago.

If they ever want to enjoy sustained success this summer, it’s something they’ll need to correct.

“When you walk people, you try to get too fine, I think,” Diekman said. “That goes for anyone. You’re … kind of pitching away from contact. That’s basically it. I feel like if you’re walking people, you’re not being aggressive. You’re nitpicking. It’s just a [terrible] part of it.”