[Syd Thrift]

As far as the "rust" aspect goes, I'm pretty sure that as soon as a player gets a single appearance, the rust falls off, although of course it can accumulate between that point and their next outing. Rust also IME affects injury proneness much more than actual ability and so in turn the most dangerous appearance for a player in ST will always be their first. Generally speaking, I think that if you're doing something where all the players who figure to be on your Opening Day roster get some use, you should be OK here.

Personally I don't pay super duper hard attention to ST except that I tend to use it to make a final determination as to who gets a job - it's preferable to me to doing a coin flip, basically (although sometimes you get a situation where one guy hits .260 and the other one hits .255 and you're right back to where you started).

There's also the fact that ST is the best time to train a player at a new position - I think every appearance counts, and not only that but it counts something like 3x as much as it would if you started them at said position in the regular season. I don't use this enough but especially if you have, like, a longtime outfielder whom you want to drop down to first base because you've got rangier guys to play at their old position, start them at first every game of ST and see where they are by the end of it. And of course IME younger players often don't have a lot of versatility so sometimes if you have a SS-only guy, you might want to put them out at 2B every game just so that you can have the choice to use them there once the season starts.