Outfielder A.J. Pollock was also caught off guard.
"I was stunned," he said. "Really don't have any words to describe the fact that we're getting Greinke. I guess the first thing that went through my head was I'm absolutely ecstatic that I don't have to face him."
Pollock is 3-for-12 in his career against Greinke.
"He's a nightmare to game plan for," added Pollock. "For me, he's the toughest pitcher to face in the league.