The definition prior the one you referenced says "an undersized or insignificant person". Thats not how I would describe Anderson. And if you go to urban dictionary its a lot worse. Just a matter of semantics and opinion I guess but I always took the term "scrub" as a pretty big diss - however I could be wrong.Scrub - noun - A player not on the varsity or first team.
I don't have the same reaction to the term. It's hard to descriand bench players and not have any negative connotations.
Fwiw - maybe those players were scrubs but we'll never know since Nick failed to mention the names who combined to score the five runs.