SAN DIEGO – In signing Corey Kluber to a one-year, $10 million contract in the offseason, the Red Sox were confident they were gaining a starter who would consistently keep them in games. They were confident they were adding a starter who would pound the strike zone.

Nine starts in, Kluber isn’t doing either of those things with any frequency. The veteran can only hope that his outing Sunday afternoon in a 7-0 loss to the Padres at Petco Park, in which he lasted a season-low of 2 1/3 innings, will wind up as his nadir for 2023.

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“Frustrating for me, frustrating for everybody,” Kluber said. “Just doing a poor job of finding the correct adjustment to make. I'm trying to do stuff to try to get it done when I’m out there and not quite being able to do it.”

Though the Red Sox are gaining another starter later this week when Garrett Whitlock is activated from the injured list for a likely turn on Saturday in Arizona, it won’t come at the expense of Kluber (2-6, 6.26 ERA), who will make his next start.

Manager Alex Cora said he will give the ball to Kluber for the finale of this nine-game road trip on Sunday. The Sox will use six different starters for the final six games of the West Coast swing.

The manager was asked if he was going with a six-man rotation for the foreseeable future.

“For the foreseeable week, put it that way,” Cora said.

It wasn’t that long ago that Kluber was more than holding his own. Last season with the Rays, he allowed two earned runs or fewer in 18 of his 31 starts. 

That version of Kluber hasn’t arrived yet.

The frustrating thing for Kluber and the Red Sox on Sunday was that the Padres -- a team that had been struggling mightily for wins and runs of late -- scored four times in the first inning without having to do that much. 

Kluber issued three walks and made a fielding error en route to throwing 40 pitches in the frame. One of his free passes came with the bases loaded.

“Command was off. That’s something that’s not him,” Cora said. “We've been battling with this early in the season. It’s something we’ve tried to correct, but today, the walks put him in a bad spot.”

Despite all this, Kluber was one pitch away from escaping the inning with just one run allowed. Then Rougned Odor, the seventh batter of the inning, turned a 1-2 count into a full count and provided the first hit and biggest hit of the day for San Diego, a damaging three-run double to right field.

“Just a slider that didn’t really get to the right location, and kind of stayed middle and he was able to keep it fair,” Kluber said.

The coaching staff has been working with Kluber between starts on two specific things – improving his command and regaining the bite on his sinker.

“I think that there's probably some getting in my own way, trying to make too many adjustments,” Kluber said. “And then you try a balancing act of finding the right one. I think it boils down to doing a better job of figuring out how to do it.

“I wish there was one thing because I feel it’d be easier to be able to make the correction. Like I said, not something I’m accustomed to doing, definitely frustrating but just got to keep working at it."

The coaching staff is just as frustrated not being able to unlock Kluber to this point of the season.

“If I knew, I’d put it in a bottle, drink it and throw strikes over there, to be honest with you,” Cora said. “We’re working hard with him because we know when he’s around the zone, he’s tough to hit. We’re just putting ourselves in a bad spot. ... After that [first inning] he kind of settled down, but the damage was done. We'll keep working.”

The 37-year-old Kluber will go back to the drawing board in hopes that next Sunday will be a lot better than this one.

“Just trying to work my way out of it,” Kluber said. “That’s the only choice. Giving up isn’t an option, obviously. I think the only way that I know how to try to get myself out of it is keep working through it -- keep trying to find that right adjustment and having a belief that it will come sooner than later.”