SAN DIEGO -- All that progress the Padres made offensively on their road trip? It seemed to vanish once they returned to Petco Park. It has been that way far too often this season.

The Padres opened a crucial six-game homestand with a dud against the D-backs on Monday, a 5-0 defeat in which they were blanked for seven innings by rookie Ryne Nelson in his Major League debut.

“We’ll have good games, we’ll have bad games,” said Padres manager Bob Melvin. “But we just haven’t gotten to a point yet where we’ve gotten into a rhythm and put pressure on pitchers -- and done it multiple days in a row.”

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The loss, coupled with a Brewers win in Colorado, meant the Padres’ lead in the Wild Card race dwindled to two games -- just one in the loss column. San Diego also dropped into the third and final NL Wild Card spot, now trailing Philadelphia, having lost the head-to-head tiebreaker. A month of regular-season baseball remains.

“We’re still right there,” said Manny Machado, whose rare off performance snapped a nine-game hitting streak. “We’re still in the fight. As long as we stay right there, that’s all that matters. It’s about getting in and getting hot at the right time.”

Offensively, the Padres finally seemed to be putting it together on their recent road trip. In nine games -- even at a trio of relatively pitcher-friendly ballparks -- they scored 51 runs.

That made Monday’s struggles all the more perplexing. Jurickson Profar doubled twice, including a gapper to lead off the game. The rest of the San Diego offense combined for two hits. 

“There’s going to be good days, there’s going to be bad days,” Machado said. “... It’s just about putting this one behind us.”

Lately, the Padres have gotten too much of the latter -- particularly at Petco Park, which has been the toughest venue to score in, according to basic park factor. On Aug. 10, the Padres scored 13 runs in a win over the Giants. In seven home games since then, they’ve combined to score just nine runs.

Monday’s listless offensive performance wasted another excellent start from left-hander Blake Snell, who has been perhaps the Padres’ best pitcher in the second half. He struck out 10 hitters across six innings of one-run ball, commanding his fastball expertly and pairing it with a dominant, putaway slider.

“You can’t get upset at not scoring runs,” Snell said. “This team is going to score a lot of runs. We’re really good offensively. It’s tough that it has to be the day that I’m pitching. But I know the next time I pitch, they’ll score a bunch of runs and help us win.”

The Padres, of course, are presently without two crucial right-handed bats. Wil Myers remains day to day with neck tightness, and after the game, manager Bob Melvin revealed that Myers wasn’t available on Monday. Even more concerning: The team placed Brandon Drury on the seven-day concussion IL prior to the game, and there’s been no indication of when he might return.

With limited options, the Padres started Matt Beaty at designated hitter on Monday. And, in perhaps the game’s most crucial situation, Beaty’s spot came up.

Trailing by two runs, the Padres put two men aboard with two outs in the seventh. On a different day, that would’ve been Myers or Drury’s spot. But the Padres’ bench is thin, and Beaty was the only left-handed option.

“Left-handed hitter, right now he’s finally healthy again,” Melvin said. “There weren’t [other] options at that point. He was going to hit regardless.”

The Padres did have a handful of right-handed bats on the bench, but Melvin said he didn’t love those matchups against the righty Nelson. If he had, Melvin pointed out afterward, Beaty wouldn’t have started in the DH spot against Nelson in the first place.

Beaty worked himself a favorable 2-0 count, but flied harmlessly to right. The Padres never seriously threatened after that, as their bullpen allowed four runs across the final three innings. 

The Padres have a month -- and 17 of their final 26 games at Petco Park -- to sort out their offensive issues.

“We only have so many days left,” Melvin said. “But it is what it is. We expect to do better than we have. We expect it, any particular day, to break open. And there have been days where that’s happened. But not enough.”