Nieuwenhuis hit solo homers in the second and fifth innings and added a two-run shot in the third as part of a four-RBI day that ended an otherwise rough first half on a storybook note. Entering play Sunday, Nieuwenhuis sported just a .091 batting average.
"That's why it's a great game," Mets manager Terry Collins said. "You don't have any answers for it. Nobody knows what is going to happen on a daily basis."
That quickly changed when Nieuwenhuis lined two opposite-field homers in his first two at-bats against D-backs starter Rubby De La Rosa. Lefties entered play hitting .298 against De La Rosa, which prompted Collins to start Nieuwenhuis and let right-handed-hitting Michael Cuddyer rest his still sore left knee. Collins looked like a genius when Daniel Murphy added to Nieuwenhuis' barrage with a solo homer of his own. The Mets' last 15 runs have come via the long ball.
De La Rosa lasted just 3 2/3 innings and took his fifth loss, while Niese improved to 5-8 by holding Arizona to three runs in 6 2/3 frames. Jenrry Mejia recorded an out in his season debut, Bobby Parnell survived a scoreless eighth and Jeurys Familia recorded his 27th save to give New York its seventh win in nine games headed into the All-Star break. Arizona received a solo home run from All-Star first baseman Paul Goldschmidt.
"The guys battled," D-backs manager Chip Hale said. "Again we had the tying run come to the plate. Niese did a nice job of mixing speeds and locations and Goldy hit the home run and we had some good at-bats, I thought."
MOMENTS THAT MATTERED Niese in solid form: The lefty wasn't as dominant as he was in his last start, but recorded his second consecutive win. Niese struck out three and didn't walk a batter, while recording nine ground-ball outs. He also slapped a single to left, making it four straight games Mets pitchers have recorded a hit.
"It was a good way to end the first half," Niese said.
Rubby struggles: When a game gets away from De La Rosa, it can happen in a hurry. In a four-batter span in the third, the game went from being tied at 1 to the Mets hitting a pair of homers and scoring three runs to take command.
"Today wasn't my best day," De La Rosa said. "I think, in trying to keep the ball down, I kept a couple of balls up and I paid the price for that." More >
Mejia makes debut: Mejia was reinstated from his 80-game PED suspension on Tuesday, but hadn't appeared in a game yet due to consecutive strong outings from Mets starters. Collins insisted before Sunday's game that Mejia would pitch no matter what, and he did. Mejia stranded a runner on second when he retired Chris Owings, representing the tying run, to end the seventh. It was Mejia's first Major League action since Sept. 28 of last season. More >
Goldy ends HR drought: Goldschmidt hit his 21st home run of the season in the fourth, his first since June 24. The solo shot snapped his homerless plate-appearance streak at 71.
"[Niese] was working down all day and that one was up and, fortunately, I was able to hit it hard," Goldschmidt said.
"I'm just happy. Just happy to be back with these guys, to go to battle with them and be back there on the field." -- Nieuwenhuis, on his roller-coaster season
SOUND SMART WITH YOUR FRIENDS
Nieuwenhuis became the 10th Mets player to hit three home runs in a game, but just the first to do so in a home contest.
UPON FURTHER REVIEW
The umpires convened in the second inning to make sure Nieuwenhuis' first homer cleared the orange indicator outlining the top of the left-field fence. After a crew-chief review of 46 seconds, the call was confirmed as a home run. His other two blasts proved less debatable.
WHAT'S NEXT D-backs: The D-backs open the second half Friday night against the Giants at Chase Field, with first pitch at 6:40 p.m. MST. Lefty Robbie Ray will get the start for the D-backs in his first career appearance against San Francisco.
Mets: New York enters the break with a winning record for the first time since 2012. The Mets are 47-42, two games back of first-place Washington. They will kick off the second half with a three-game series against the Cardinals at Busch Stadium, starting Friday at 8:10 ET.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. Joe Trezza is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.