LOS ANGELES -- After throwing 106 pitches against the Yankees on June 7, Yoshinobu Yamamoto reported some soreness and tightness around his right triceps area.

Given that information, the Dodgers decided to push Yamamoto¡¯s next start back from Thursday to Saturday in hopes that a few more days off would get the right-hander back on track. But unfortunately for the Dodgers and Yamamoto, that plan didn¡¯t work out the way they hoped.

Yamamoto reported some more discomfort after his second inning of work, cutting his outing short in the Dodgers¡¯ 7-2 loss to the Royals at Dodger Stadium. The team announced Yamamoto¡¯s injury as right triceps tightness.

Dodgers manager Dave Roberts said Yamamoto will get further testing done on Sunday and a stint on the injured list is a ¡°high possibility,¡± even if it¡¯s just for precautionary reasons.

¡°I was feeling it a couple days ago, but today, that tightness was gone, and during the game, my triceps tightened up,¡± Yamamoto said through interpreter Yoshihiro Sonoda.

The Japanese rookie said he felt tightness in his triceps as he warmed up for the game. He notified the coaching staff, but added he felt confident he could have made a regular start despite the discomfort.

Roberts said they were aware of Yamamoto¡¯s soreness throughout the week, which is why his start was pushed. Had Yamamoto complained more about soreness heading into Saturday, the Dodgers would have made the decision to scratch the 25-year-old.

¡°We wouldn¡¯t pitch him if we felt he was going to put himself in harm¡¯s way,¡± Roberts said. ¡°My time here, there have been starters that haven¡¯t made a start that day because they couldn¡¯t make the start and we¡¯ve had to pick up the pieces on pitch one. That wasn¡¯t the case [Saturday], to my understanding. I¡¯ll talk to Yoshinobu myself to get the exact communication, but again, I¡¯ve never put a guy out there that is going to get hurt.¡±

Yamamoto¡¯s issues started during his previous start at Yankee Stadium. Yamamoto threw his 19 hardest pitches, consistently getting to 97-98 mph with the four-seam fastball. He also threw 13 sliders against New York, his most in a Major League game.

During the week, Yamamoto had lengthy conversations on the field with the trainers, coaches, general manager Brandon Gomes and even his agent, Joel Wolfe. All parties involved determined that Yamamoto wasn¡¯t going to pitch on Thursday, instead going on Saturday.

But from the start against the Royals, it was evident Yamamoto didn¡¯t have his best stuff. His four-seamer was down 1.4 mph from his season average, while his curveball and splitter were also affected with lower velocity and spin rate.

Yamamoto¡¯s last pitch of the night was a 93.3 mph four-seamer. After the second inning, SportsNet LA cameras caught pitching coach Mark Prior running over to Roberts to let him know to come into the tunnel. That¡¯s when, Roberts said, he found out the extent of Yamamoto¡¯s discomfort.

¡°I was surprised,¡± Roberts said. ¡°He¡¯s been obviously very durable throughout his entire professional career. I think we¡¯ve been very good as far as managing usage and the days. Yes, I was very surprised. Again, if [we knew] he was going to go two innings, he wouldn¡¯t have started tonight.¡±

Given how sudden Yamamoto left the game and the lack of velocity, the initial diagnosis of a triceps injury could be good news, though neither Yamamoto nor Roberts ruled out any other damage until the team doctors check him out on Sunday.

¡°Until we know information, that¡¯s kind of what he said he feels and right now we¡¯re all going by what he¡¯s saying and what he¡¯s feeling,¡± Roberts said. ¡°We¡¯ll get our doctors involved, obviously, and see if there¡¯s more to it.¡±

Losing Yamamoto for an extended period of time would be a significant blow to the Dodgers¡¯ rotation. Yamamoto, the team¡¯s $325 million acquisition this winter, has been putting together a strong rookie season, posting a 2.92 ERA through 14 starts. The Dodgers already have starters Clayton Kershaw and Bobby Miller on the IL, though Miller is scheduled to make his return next week against the Rockies at Coors Field.

Now, he¡¯ll presumably be taking Yamamoto¡¯s spot in the rotation, at least in the short term.

¡°The last outing was not directly related to this tightness, it¡¯s more during the recovery process this week,¡± Yamamoto said. ¡°I think I will do a little more examination, but the actual feeling I¡¯m having is not that bad.¡±