NEW YORK -- So devilish was Jacob deGrom’s slider on Thursday that when he bent one toward the inside corner in the second inning, Padres catcher Francisco Mejía hacked at it, lost his balance and fell to the dirt, his helmet spinning to rest beside him.

“That was probably my best slider of the day,” said deGrom, who had plenty to choose from. San Diego had no answer all afternoon for deGrom’s slider, which he threw a career-high 56 times in leading the Mets to a series victory with a 4-0 win at Citi Field.

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“It’s a devastating weapon when he’s got it going on,” Mets manager Mickey Callaway said. “Even when it’s not at its best, it’s still probably a tick above average. When it’s like what it was today, it’s probably the best slider in baseball.”

For the first time in his career, deGrom threw more sliders than fastballs, pounding them mostly inside to left-handed batters. The strategy echoed an overall uptick in slider usage for both deGrom and teammate Noah Syndergaard under new pitching coach Phil Regan, though on this day, the reigning National League Cy Young Award winner took it to an extreme, recording seven of his nine strikeouts with that pitch.

In that fashion, deGrom blanked the Padres over seven innings to pick up his second win in three starts since the All-Star break. All of his support came in the first inning, when the Mets scored four times on a Wilson Ramos sacrifice fly, a Todd Frazier two-run double and a Michael Conforto RBI hit. Frazier, who has an outside chance to be traded before the July 31 Deadline, reached base in four of his five plate appearances.

But Frazier did not have to face deGrom’s slider. If he had, he may have suffered the same fate as the middle third of San Diego’s lineup, which finished 0-for-9 with five strikeouts against deGrom. For left-handed hitters such as Eric Hosmer, the slider whipped toward them as deGrom spotted it consistently on the inside corner. For right-handed hitters like Hunter Renfroe, it faded away after coming out of his hand looking like a strike at an average of 90 mph.

“It's hard. He throws it hard,” Renfroe said. “It's right off his fastball. It doesn't necessarily have a lot of depth to it or anything like that. Just enough to keep you honest, and it's right off the fastball. ... He threw it really well today.”

Although deGrom’s slider percentage has increased in general since Regan took over as pitching coach in June, both he and Regan insist that’s been a matter of reacting to swings more than a premeditated plan. The slider isn’t about to become deGrom’s primary pitch on a regular basis -- “not when you throw 98 miles an hour and locate where he locates,” Regan said. But it is something he appears committed to for as long as opponents are waving and missing and falling in the dirt.

“To me, I feel like it looks just like my fastball, down and away,” deGrom said. “You throw a pitch down and away, they take it, and then you throw a couple sliders, and it looks like the fastball. I’m getting swings and misses on it. That’s what I’m seeing out there, and just going on what I’m seeing.”

“A good pitcher will know what’s working for him that particular day,” Regan added. “It’s just what you feel that day, and what’s working for you that day. Today, he had a great one.”

Consider the National League on notice. Even before his slider uptick this month, deGrom had been thriving; he’s recovered from a disappointing April to post a 2.36 ERA since the start of May, giving himself at least an outside chance to make a run at defending his NL Cy Young Award. The slider simply gives him another top weapon to achieve that goal.

“He’s our ace. He sets the tone,” Callaway said. “He has for a long time in this organization now, and he’s going to be here a lot longer doing the same thing. He means the world to us, and that’s why we wanted him here as long as possible.”