Uh oh.

Spring training has barely begun, and it's already time for A's fans to hold their collective breath. Manager Bob Melvin divulged some injury news Tuesday, and it's not what you want to hear.

Melvin told reporters that starting pitcher A.J. Puk has a mild shoulder strain. An MRI revealed no structural damage, but Oakland is temporarily shutting down the young phenom as a precaution.

Puk, 24, made his MLB debut with Oakland last season, going 2-0 while posting a 3.18 ERA with 13 strikeouts across 11 1/3 innings. The former first-round draft pick is expected to be a major part of what should be a very formidable A's starting rotation this season, alongside Sean Manaea, Frankie Montas, Mike Fiers and fellow rookie Jesus Luzardo.

[RELATED: Luzardo, Puk plan to be roommates in Oakland this season]

He previously underwent Tommy John surgery in April of 2018, forcing him to miss the entire season. Puk has all the arm talent in the world, and Oakland is right to be taking it extra careful with him.