Interference or No?
 

Batter squibs a ball that hugs the 1st base line. He runs to first and about the time he catches up to the ball he hit (just before the running lane), the pitcher arrives to field the ball. The pitcher slows down almost to a stop to avoid running into the batter. The ball ended up going foul. The next pitch the batter grounded out to first. Had the pitcher been able to field the ball, it would have been fair, but he "chose" to let it go (either because the batter-runner made him break stride OR to let it roll hoping it would go foul).
Could interference have been called?

JJ

Of course. Interference is a dead ball, so if it was called, the fact that it rolled foul is immaterial. PS - running lane is immaterial here. All that matters is --- did he interfere with the pitcher's ability to make a play (while the ball was in fair territory).

If the ball was fair when that happened, the batter-runner definitely interfered with the pitcher.

Where it gets dicey is when the ball was in foul territory when the pitcher stops to avoid the batter-runner, and then the ball ends up fair. Do you rule interference if the batter-runner prevented the fielder from touching a batted ball to make it foul?