"It's not very severe, but still you don't know how long it takes so we'll just have to wait and see," McDonald said. "Until I swing pain free, it does me no good to rush a time frame."
The D-backs did not waste any time. They placed McDonald on the 15-day disabled list.
It turns out the injury was not recent. McDonald said he thought it happened when he tried to break up a double play while the team was in Kansas City in mid-May.
"It's just been nagging ever since," McDonald said. "It finally got a little worse and I couldn't get it out of there."