SAN DIEGO -- The Padres’ offense was already struggling.

Then, moments before first pitch Tuesday night, star right fielder Juan Soto was scratched with left mid-back tightness. An hour after that, Brandon Drury was ejected for arguing what appeared to be a missed call.

And sure enough, the offensive struggles continued in San Diego, as the Padres dropped their series opener to the Guardians, 3-1, at Petco Park.

After the game, Soto seemed relatively optimistic that the injury wouldn’t linger, calling it, “Nothing crazy.” His back flared up while he was swinging in the batting cage shortly before first pitch. During the game, Soto took further swings in the cage, hoping he might get a chance to pinch-hit, but he wasn’t able to.

“I’ve never had a back issue, so it was kind of new for me,” Soto said. “It’s pretty tough. I tried my best to go out there.”

The Padres, who have scored nine runs in five games during their current homestand, need a healthy Soto as soon as possible. But manager Bob Melvin expressed caution, noting that it’s unlikely Soto would play Wednesday afternoon and that he would be re-evaluated after the team’s off-day on Thursday.

“We’ll see how he responds,” Melvin said. “He felt a little better after treatment today. … Any time you lose a player like that from your lineup, it affects you. But there’s not much you can do about it. Someone else gets an opportunity, and you move forward.”

Adding insult to injury, Drury -- another Trade Deadline acquisition who has been scuffling lately -- was punched out on what appeared to have been ball four during his at-bat in the fourth inning. After checking his swing on a pitch, which was low and away, Drury took two steps toward first base before he realized he’d been rung up. 

Drury turned to home-plate umpire Stu Scheurwater to express his displeasure, and after a brief exchange, Drury was ejected for the first time in his career.

“I’ve been grinding lately,” Drury said. “I’ve been working hard to get myself back on track, and I had a tough first at-bat today. Second at-bat, I thought I earned a walk. I fought back from two strikes, and I’m running down the first-base line, because the pitch wasn’t even close. And he rings me up. 

“I was just almost shocked and mad at the same time, and I kind of snapped. ... But I thought it was a little bit of a short leash, especially with how far out of the zone that pitch was.”

When it rains, it pours. The most maddening aspect of the Padres’ offensive struggles is this: Their on-base percentage ranks seventh in the Majors. Their 453 walks trail only the Dodgers and Yankees. They get plenty of baserunners -- and often don't do enough with them. No team in the Majors has stranded more runners this season than San Diego.

The Padres tacked on 10 more to that total on Tuesday, going 1-for-8 with runners in scoring position.

“Again, we got some guys on, and we couldn’t get them in,” Melvin said. “That’s been the biggest problem. We seem to draw some walks and get some guys on base. It’s a kind of a continued problem, where we haven’t gotten them in.”

In a way, those struggles can be tied to the makeup of this roster. The Padres have an abundance of pesky hitters who work counts and fight their way aboard. For much of the year, however, they simply didn’t have enough hitters who could slug.

That’s why they traded for Soto, Drury and Josh Bell. Yet, the RISP woes remain just as pronounced.

“You can’t put too much pressure on yourself, trying to do too much,” said second baseman Jake Cronenworth, who drove in the team’s only run with a fifth-inning single. “Doesn’t matter whether the guy’s on first base, second base, third base, you’ve got to go up there and execute the plan. Right now, we’re just in a little bit of a lull, where we’re going up there and guys are trying to do too much.”

Padres right-hander Mike Clevinger was sharp across six innings, facing his former team. He gave up only two hits, but both were solo home runs. Oscar Gonzalez took him deep in the second and Andrés Giménez did so in the fifth.

These days, the Padres are getting plenty of solid starting pitching. And too often, like Tuesday, they’re letting it go to waste. A win would have given San Diego an extra game of breathing room on Milwaukee. Instead, its lead remains 1 1/2 games over the Brewers in the race for the third National League Wild Card spot.

“Any loss sucks,” Clevinger said. “Especially now that we’re in this stretch. Every game is semi-must-win for us. It doesn’t matter who we’re playing. It’s time to get going.”