When must an offensive sub be named (ASA)?

[Infield Fly]

Question came up at our ASA class last night. Opinions were split.

A runner is ejected for flagrantly running over third baseman. The offensive team started the game with nine players and has no subs available.

When do they have to name the (non-existent) replacement for the ejected player?

It's the bottom of the 7th, tie score.

If before the next pitch, by Rule 4 D 2 a they are not allowed to drop down to continue to play with 8 because of the ejection. So they would forfeit the game.

If not until that spot comes up again in the batting order or until they were to take the field for the next inning, then they could potentially score a run before having to name a replacement due to either needing a batter for that spot in the order or a 9th fielder.