PHOENIX — Even in the best of times, Mets slugger Lucas Duda is soft-spoken and reserved. He prefers measured tones. But after a 5-4 loss to the Diamondbacks on Tuesday night, even he had to break from form.

On a night in which he faltered in two critical points, Duda nearly raised his voice as he offered a scathing review of himself.

Indeed, in shades of the 2015 World Series, he made a poor throw home that cost the Mets a run in a one-run loss. Before that, Duda struck out with runners on second and third, part of a second inning in which the Mets had Zack Greinke on the ropes but managed just one run.

“I’ve got to clean it up, man,” said Duda, who is just 2-for-13 in four games since coming off the disabled list. “I’ve been bad at baseball for the past week.”

Not that Duda has been alone. The Mets (16-22) have equaled a season high by losing six straight games. They dropped six games below the .500 mark for the first time since Sept. 26, 2014.

Now, the Mets must win Wednesday’s series finale to spare themselves a winless six-game road trip and a seven-game skid, which would be their longest since a June swoon in 2015.

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“When things aren’t going good, nothing goes good,” manager Terry Collins said.

Before the game, the Mets reshuffled their roster, signing veteran righthander Neil Ramirez to bolster a beleaguered bullpen.

Ramirez, 27, is hardly a cure-all. In nine appearances with the Giants this season, he allowed 10 runs in 10 1⁄3 innings (8.71 ERA), though he has struck out 18 batters while walking just four. The Blue Jays claimed Ramirez off waivers but designated him for assignment before he pitched in a game.

“Every mistake I did make was getting hit,” said Ramirez, who at the very least provides a fresh arm for a Mets bullpen that has paid dearly for the rotation’s shortcomings.

Then, the Mets finally added Asdrubal Cabre ra to the disabled list, ending an ill-fated effort by the shortstop to play through a sprained left thumb.

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“You guys know me, I like to play, I want to be in there,” said Cabrera, whose DL stint has been backdated to Sunday, meaning he could return in a week.

Nevertheless, despite taking steps to fortify themselves, the Mets’ tailspin continued.

Lefthander Tommy Milone extended what has become an infamous streak for a starting rotation that has devolved into one of the worst in baseball. By allowing five runs in 5 2⁄3 innings, Milone ensured that it would be 16 straight games since a Mets starting pitcher recorded an out in the seventh. During that stretch, Mets starters have combined for a 7.10 ERA.

Still, the Mets picked away, closing the deficit to 5-4 in the seventh when Rene Rivera continued his unexpected offensive surge. His two-run shot pushed his career-best hitting streak to 10 games and brought the Mets to within a run. Earlier, Curtis Granderson walked with the bases loaded and hit a solo homer while hitting eighth for the first time since 2011.

Relievers Paul Sewald combined with Jerry Blevins and Fernando Salas for 2 1⁄3 innings of scoreless relief. But the Diamondbacks’ Fernando Rodney closed out the Mets the ninth.

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In the end, Duda fixated on one mistake.

The Diamondbacks seized a 4-1 lead in the third off Milone while opening up some old wounds. Gregor Blanco had already singled home a pair of runs, and then scored on an RBI single by Chris Owings, when the Diamondbacks tacked on another run when Paul Goldschmidt stole home on the back end of a double steal. He was safe because Duda made a wide throw home.

“Terrible throw,” he said. “Terrible.”