SEATTLE -- Justus Sheffield’s struggles have become so pronounced that his spot in the rotation is likely in jeopardy heading into the All-Star break. His latest setback was arguably the worst start of his young career, and it led to a 12-1 Mariners defeat at the hands of the team that traded him to Seattle in 2018.

But Sheffield suggested postgame that he’s dealing with a health issue. He said after his 1 2/3-inning outing, in which he gave up six earned runs, that he has spent more time in the athletic trainers’ room trying to put his body in better positions to pitch. Sheffield said that his soreness isn’t arm-related, but rather, general body issues.

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That, plus his poor results over an incredibly tough month, only exacerbated his shaky status within the rotation.

“I didn't really feel 100 percent,” Sheffield said. “ So I’ve just got to get right and get back out there to where I can compete. Just body-wise, I’m fighting through some stuff. ... I've been in the training room working on some things, getting some stuff right. So hopefully, we'll figure it out and maybe I'll be able to get into positions I need to get into.”

Mariners manager Scott Servais said that the club would take the next few days to determine how to handle Sheffield’s next scheduled start on Sunday against the Angels, the final game before the All-Star break.

“At the end of the day, we need to do what's best for the player and obviously the team along with that,” Servais said. “But we’ve got to get Sheff going in the right direction again. We'll sit down and talk about it in the next few days. That turn does come around again on Sunday before the break, and we'll make the best decision for everybody involved.”

But if health is a concern, that would in part explain what’s been a downward trend for the 25-year-old, who has now had glaring issues in five straight starts. In this stretch, he’s gone 0-4 and has given up 24 earned runs in 19 innings for an 11.36 ERA, raising his season ERA from 4.77 to 6.48. Tuesday’s start was the shortest of his career.

For the season, Sheffield has given up 14 homers in 73 2/3 innings -- including a 434-foot three-run shot that Giancarlo Stanton rocketed 115.8 mph off the bat in the first -- after giving up just two in all of 2020.

Sheffield has mostly avoided injury since he was drafted in the first round by Cleveland in 2014. The last time he was on the injured list was in ‘18, when he was shelved 11 days with shoulder tightness while pitching for the Yankees’ Triple-A affiliate. He missed two months in ‘17 with an oblique injury.

“I come in and I bust my [tail] and work hard on the things that I think will be corrected that could help me in my next outings,” Sheffield said. “But honestly, I think sometimes it can be overdoing things, trying to figure it out, when really, there's nothing really to figure out. It's just the game of baseball.

“I feel like earlier my starts didn't really go my way, but I threw the ball pretty well. ... So then I go back to the drawing board and try to nitpick every little thing mechanically and things like that I did wrong or could fix or that's the problem. But honestly, I don't think that any of that was the problem or issue.”

Coupling his health with a player-development perspective, continuing to roll him out there could have a prolonged negative impact.

Sheffield has Minor League options should Seattle opt to send him to Triple-A Tacoma for a reset. But with the Mariners already down from a six-man rotation to five with Justin Dunn sidelined due to right shoulder inflammation, the replacement options for Sheffield are limited.

That could be further compounded when MLB hears the appeal for Héctor Santiago’s 10-game suspension, which is expected to take place this week. If Santiago’s sanction is upheld or even reduced to fewer games, the Mariners still won’t be able to fill his roster spot, which would put the bullpen down an arm.

That leaves Robert Dugger as the likeliest candidate for Sunday, but even he would simply be a short-term fix given that he’s only been stretched out to four innings this season. Jimmy Yacabonis is another starter at Tacoma, but he’s not on the 40-man roster.

Trade for a Minor League starter to fill in? Stretch Dugger out? Wait out Santiago’s possible suspension? The Mariners’ starting-pitching depth became a glaring concern in April and May, when James Paxton, Nick Margevicius and Ljay Newsome were all lost to the 60-day IL, and that issue could be coming to a head again.