Why did HAL put Cassidy in?

https://onlinegames.strat-o-matic.com/game/449154/590

Joe Cassidy is on my team strictly as an injury replacement who can hit an occasional triple. Yet last night HAL decided to install him as a defensive replacement (apparently) in the above game.

NOTE:
Neither of my platoon shortstops are designated to be removed for a sub.
Cassidy is NOT set to sub in defensively at shortstop.
No one was injured.

So WHY did HAL put Cassidy in? It didn't affect anything but I found it very odd?????

Cassidy is the best defender of the 3 shortstops you have. I have noticed HAL making more unsolicited defensive substitutions recently, so this was HAL deciding what he thought was the best move.

Actually I find it odd that Harrelson replaced Cassidy in game 98 starting the 9th.

I hadn't noticed that. Yeah, that is odd. Lots of weird stuff happening on the defensive side lately it seems.