The very start of the latest trailer for the upcoming Ender's Game movie features Mazer Rackham and Colonel Graff sitting across the table from one another:

Rackham: He's not ready.

Graff: You're never ready. You go when you're ready enough.

I don't recall the two of them ever having a conversation in either Ender's Game or Ender's Shadow. Or am I misremembering?