PHOENIX — The Arizona Diamondbacks had Sunday laid out perfectly before blowing a lead and the game against the Boston Red Sox, 7-4.

The New York Mets and San Francisco Giants lost. The Diamondbacks would have jumped the Giants with a win and climbed to within 3.5 games of the postseason picture.

Arizona held a 3-1 lead after starting pitcher Ryne Nelson gutted out a quality start with six innings and one earned run.

Instead, sloppy defense and poor execution from the bullpen took a toll. The Diamondbacks (72-72) allowed six runs in the final three innings, as the Red Sox (79-65) avoided the sweep.

Sunday was a damper on what had been a terrific homestand. Arizona went 4-2 against teams pushing for postseason spots, but the ugliest aspects of this season popped up at an inopportune time again.

“This was an extremely frustrating loss,” manager Torey Lovullo said. “To get to where we’re going, you can’t do the things I saw us do out there today. We’ve got to execute at a much higher level. We have been, and that’s why we’ve been winning games. When you make plays like we made today and give a good team five outs in one inning, you’re not gonna win a lot of baseball games.

“It’s September baseball. We’re chasing something. It’s gotta be crisp, it’s gotta be focused.”

The top of the seventh inning was downright horrific, starting with Ryan Thompson hitting Trevor Story with a pitch. The Diamondbacks challenged the hit-by-pitch and lost.

Thompson then had Story picked off, but first baseman Tyler Locklear took too long to release the ball on the rundown, and the runner was safe at second.

Story would score on a David Hamilton single, and two more runs came home on a two-out throwing error from third baseman Jordan Lawlar. It was not a great moment for the young corner infield.

Sox jump ahead 4-3 in the seventh 🍿 pic.twitter.com/LcG9WPJwxw

— NESN (@NESN) September 7, 2025

“It’s probably a drop-step, one-handed play,” Lawlar said he’d do differently. “Recovered, caught it and gripped a two-seamer, put some pace on it and the two-seam ran a little bit on me.”

Lawlar drove in the game-tying run in the bottom half with a single for a bit of redemption, but the D-backs stranded two runners. Top two hitters Geraldo Perdomo and Ketel Marte went 0-for-8 with three pop-ups on Sunday, and Marte went hitless in the series.

In the ninth, Taylor Rashi had two runners on with two outs against pinch hitter Nick Sogard, who doubled home both runs and scored on an ensuing single. Lawlar committed another throwing error as the game seemed to really get away from a team that had been playing sharp baseball of late.

Diamondbacks’ starting rotation is humming

Nelson delivered his fourth consecutive quality start (at least six innings and three or fewer earned runs) and also the sixth straight from a Diamondbacks starting pitcher. That tied Arizona’s longest streak of the season.

In nine of Arizona’s last 11 games, its starter tossed a quality start.

Nelson had to battle for his on Sunday due to three walks, but he was helped by double plays in three straight innings. He retired his last seven batters and finished with a season-high 105 pitches.

“Didn’t quite feel like I had it all the way at the start,” Nelson said. “Defense bailed me out with some really big double plays. Then towards the end, started to feel like I slowed it down a little bit and started to execute pitches.”

His season ERA dropped to 3.48 and 3.24 as a starter.

Nelson leads the league in a stat called “wins lost,” which means he’s left the most games in line for a win only for the bullpen to blow it. He has seven this season.

Up next for Diamondbacks

The Diamondbacks hit the road for six games, starting with a critical series at the 72-71 San Francisco Giants.

The probable starting pitchers for Arizona at Oracle Park are (in order) Nabil Crismatt, Zac Gallen and Eduardo Rodriguez.

For San Francisco, Logan Webb, Robbie Ray and Carson Seymour are lined up in order.

The Diamondbacks are 4-3 against the Giants this season and host San Francisco for another three-game series starting on Sept. 15.

“ They’ve got things tightened down real nice up there, so it should be a great series,” Lovullo said.

Monday’s game begins at 6:45 p.m. MST on 98.7 and the Arizona Sports app.