Vargas had an MRI on his elbow that revealed the strain, according to Andy McCullough of the Kansas City Star.
This is the second time this season that Vargas has gone on the DL with a left flexor strain. The flexor muscle protects the UCL and the injury can be a precursor to Tommy John surgery.
Kansas City called up left-handed pitcher Brandon Finnegan to take Vargas' spot on the roster. Finnegan, who made his MLB debut just months after being drafted last year, has given up two earned runs in 9 2/3 innings this season.
The Royals (34–24) play the Cardinals in St. Louis on Saturday.
- Molly Geary