Erik Goeddel reached back and fired, hoping that his fastball would hit the outer edge of the zone. Instead, the Mets reliever missed over the plate, and a loud pop rang out over Citi Field.

Diamondbacks centerfielder A.J. Pollock hammered a two-run homer in the 10th inning, providing enough cushion to send the Mets to a 3-2 loss Monday night.

Michael Conforto’s 27th homer of the season, a solo shot to lead off the 10th off Diamondbacks closer Fernando Rodney, wasn’t enough to make up for a squandered opportunity that would loom large.

The Mets missed a chance to pull ahead in the seventh when Yoenis Cespedes ripped a bases-loaded single to left. Travis d’Arnaud scored easily to tie the score 1-1, but Asdrubal Cabrera was cut down at the plate.

Mets righthander Robert Gsellman allowed one run and five hits in 6 1⁄3 innings, an encouraging step in his second start since coming off the disabled list with a hamstring injury.

Since his return, Gsellman has allowed three runs in 11 2⁄3 innings.

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Gsellman bristled at comments by general manager Sandy Alderson, who said the righthander needed to “pitch better,” implying that his minor-league rehab had dragged on because of poor performance rather than health. Alderson was upset when Gsellman responded, “I don’t really care.” The pitcher ultimately apologized.

Notes & quotes: Just as in his previous rehab start, Matt Harvey (shoulder) pitched three innings. But this time, for Double-A Binghamton, he allowed two runs and four hits, including a homer. He walked one, struck out three and threw 54 pitches . . . Closer Jeurys Familia (blood clot) is scheduled to pitch in back-to-back games that starting Tuesday night with Brooklyn.