PHOENIX — Francisco Alvarez’s June swoon mirrored the Mets’ overall play, but suddenly the rookie catcher is eliciting oohs and ahhs from the crowd again, propping up his team along with him.

With the Mets embroiled in a back-and-forth slugfest with the NL West leader on Tuesday, it was Alvarez who created the loudest Fourth-of-July crackle with a go-ahead homer in the seventh that propelled an 8-5 victory over the Diamondbacks at Chase Field.

The Mets won their third straight — something they last accomplished on June 1 when they completed a sweep of the Phillies — and Alvarez has homered in two of those victories.

On this day, he came to the plate in a 4-4 game in the seventh and blasted a 467-foot rocket that left the bat at 110 mph for a two-run homer that gave the Mets their final lead. Alvarez’s early July thunder has followed a June in which he produced only a .534 OPS after a breakout May.

The Mets (39-46) still need plenty of victories before they can rightfully think in terms of adding significantly at the trade deadline, but the last three games have at least provided a shred of hope.

Brooks Raley, Adam Ottavino, Drew Smith and David Robertson combined to pitch the final three innings, stabilizing the Mets following Max Scherzer’s shaky performance.

Smith allowed two base runners in the ninth, prompting manager Buck Showalter to utilize Robertson for the final out.

Scherzer survived six innings, allowing four earned runs on five hits with two walks and nine strikeouts.

The Mets’ co-ace matched a season-high by surrendering three homers in his worst start in his last four.

Scherzer had pitched to a 2.25 ERA over his previous three starts to resurrect his season, which was spiraling toward the abyss.

Corbin Carroll’s homer in the first inning gave the D’backs a 1-0 lead.

The homer was Carroll’s 18th this season, a continuation of the torrid play that has placed him as the front-runner in the National League Rookie of the Year race.

Scherzer missed with a changeup that Carroll smashed over the left-field fence.

Starling Marte’s three-run homer in the fourth put the Mets ahead 3-1. Francisco Lindor walked and stole second to begin the rally and Jeff McNeil’s two-out infield single kept the inning alive.

Marte — who began the day 12-for-31 (.387) lifetime against D’backs starter Zach Davies — hit a no-doubter into the left-field seats for his fifth homer of the season.

Scherzer recorded two fast outs in the fourth before Christian Walker and Lourdes Gurriel Jr. launched consecutive homers that tied it 3-3.

The three homers surrendered by Scherzer matched his outing against the Brewers on April 4 and gave him 16 allowed in 15 starts this season.

Brandon Nimmo continued his power surge with a homer in the fifth that gave the Mets a 4-3 lead.

The homer was Nimmo’s ninth in his last 23 games and 13th overall.

Five of Nimmo’s homers have come in his last eight games. Davies had retired Alvarez and Brett Baty to begin the inning before Nimmo hit a line drive that cleared the right-field fence.

The D’backs got the run back in the fifth, but it could have been much worse for Scherzer, who struck out Walker with the bases loaded to end the threat.

The previous batter, Carroll, walked with the bases loaded to tie it 4-4 after two infield hits and a walk began the two-out rally against Scherzer, who needed 32 pitches in the inning.

Alvarez’s homer in the seventh put the Mets ahead 6-4 after Daniel Vogelbach had walked to put the go-ahead run on base.

The Mets extended their lead in the eighth by loading the bases before D.J. Stewart’s sacrifice fly brought in Lindor.

In the ninth Lindor stroked an RBI double for the Mets’ final run.