Merryweather landed on the 10-day injured list with right elbow tendinitis Monday.
The move rules the rookie out for the year, though it was backdated to Friday, so he can still return for the start of the postseason if he's healthy that soon. He'll finish his first MLB campaign with a 4.15 ERA and a 1.31 WHIP in 13 innings of work, striking out 15 while walking six.