Rule Help Needed @ Illegal Reentry

[Buddogger]

Player A is injured in field but remains in game (goes to catcher). Player A bats next inning and hits a clean single, hobbling to 1st base safely. Player A is immediately replaced on 1st base by Player B.

Question: can this be considered a legal "substitution" or must it be considered a "courtesy runner"?

The reentry of Player A is contingent upon the answer in our league as players removed for courtesy runners are ineligible for reentry.

In this case, Player A came out to catch the next inning under the substitution reentry rule. I protested siting the courtesy runner rule.

The ump claimed that it was a legal substitution as a pinch-runner and subsequent reentry but I could find no mention of the term "pinch-runner" in the ASA rule book.

4.6.c does read that any player may be removed from the game during any dead ball.

If the substitution was legal under an interpretation of this rule then that does open some interesting possibilities in the use of "pinch-runners" for players. (e.g. I stock a bench of track stars).

Thanks.