Mets starting pitcher Jacob deGrom reacts during the second inning...

Mets starting pitcher Jacob deGrom reacts during the second inning against the Milwaukee Brewers in an MLB baseball game at Citi Field on Friday, April 26, 2019. Credit: Kathleen Malone-Van Dyke

Jacob deGrom, Noah Syndergaard, Zack Wheeler and Steven Matz should be a formidable core four on the Mets’ starting staff. But they haven’t always put their best foot forward on the mound across the first month of the season.

There had been some positive signs of late from Wheeler, Matz and even fifth starter Jason Vargas. Then deGrom struggled Friday night against the Brewers at Citi Field and Syndergaard provided a replay Saturday night.

The Mets are still waiting for the rotation to display some consistency.

“This can be the best rotation in the major leagues if we continue to focus on . . . getting ahead, controlling the count,” manager Mickey Callaway said Saturday afternoon. “Obviously, you have to have your mechanics in order and you have to do all those little things, control of the running, field your position.

“But strategically, from just a pure attacking standpoint, we have to throw strike one and we have to throw 1-and-1 strikes. And if we can do that, we have the talent to be the best rotation, the best pitching staff in the major leagues.”

The starters showed up for the beginning of this 10-game homestand on Monday with a bottom-five ERA in the major leagues at 5.64. They had cut that to a still-swollen 5.17 before this latest game and moved up to 23rd. Then Syndergaard gave up five earned runs, 10 hits, including two homers, and three walks in five innings. His ERA rose to 6.35 through six starts.

DeGrom has gone from the best ERA in the major leagues last year at 1.70 to 4.85 through five outings. He’s still suffering from mechanical failure. The reigning NL Cy Young winner has lost three straight starts.

Wheeler’s five-start ERA is at 4.85, but he has thrown quality starts his last three times out.

Matz, who’s scheduled to pitch Sunday’s series finale, is at 4.03, but he has just one bad outing in five starts, his second to last outing at Philadelphia. That was the one in which he allowed six earned runs and eight overall without retiring a single batter. He bounced back by allowing one run and three hits over six innings in beating the Phillies, 5-1, Monday night.

Vargas yielded just one run in each of his last two starts, but he only went four innings and 4 1/3. His ERA is at 7.20 through four starts and one relief outing.

There is a stat that suggests there has been some bad luck involved. The rotation came into Saturday with a BABIP (batting average on balls in play) of .317, the fourth-highest mark in the majors. Last season, the starters finished 17th in BABIP at .291.

But when pitchers get behind in the count, it can lead to better swings and harder-hit baseballs. So the problems haven’t all been a function of bad luck.

“That is a big factor,” Callaway said. “We have to do a better job, because some of it is luck; some of it is us not getting ahead and they’re hitting the ball a little bit harder. More of those balls are going to fall in or get through the holes on the ground.

“So controlling the count is key. The teams that do the best job of that every year end up in the playoffs.”

The entire staff’s ERA stood at 5.35 before first pitch, which ranked 26th. Callaway said there’s a “fairly significant” difference between this year and last when it comes to the starters and relievers getting into a hitter’s count.

“The walks kind of show it at this point,” said Callaway, whose staff had issued the fifth-highest amount of walks in the NL with 98. ”We were doing good for the first week. I think we were probably one of the best. And now in the last couple of weeks, it hasn’t been great, and it’s led to some struggles.”

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