Out of left field.
in
This idiom or expression has to do with:
Something unrelated happening.
Something happening unexpectedly.
Q. Your promotion surprised everyone, including yourself, didn’t it?
A. Yeah, it came so far out of left field you would need a crystal ball to see it coming.
History:
This has its origins in baseball. One theory comes directly from the experience of players. A runner, attempting to score at home has his back to the left field, thus a throw to the plate coming from left field can arrive as a surprise to the runner.