In 2019 the best offenses got about 7000 PAs for the year (only Houston had more than that at 7078). That's 778 PAs per spot in the lineup. For ease of numbers let's do 775 PAs per position.
DH: Cruz 600
C: Garver 375, Jeffers 375
1B: Sano 600
2B: Polanco 600
3B: Donaldson 600
SS: Simmons 600
LF: Kiriloff 600
CF: Buxton 600
RF: Kepler 600
That's a reasonable estimate of what the Twins can expect on average (Buxton clearly high, but others low and am just trying to make it easy on the math). So of the 7000 PAs those 10 guys are covering all but 1450 PAs. I have to assume they're going to want to get Arraez basically the same amount of work as the rest of those guys so that's another 600. So their main 11 guys are covering all but 850 PAs with them averaging about 120 games each(7000 PAs averages out to about 5 PAs per game per lineup spot so 600 PAs is about 120 games).
That is a general way to account for some minor injuries here and there, some regular scheduled rest, and a major injury or 2 (looking at you Buxton). That's 1320 games played/started by those 11 guys. Out of 1458 total games played for the 9 lineup spots. We're left with 138 starts and 850 PAs for 4th OF, 26th man, and injury call ups. Have to assume Cave gets about about 75 starts (had 91 in 2018 and 72 in 2019) which gets him 375 PAs. So now we're at 63 starts and 475 PAs for 26th man and injury call ups.
Let's assume Astudillo is our 26th man for the sake of this argument. Let's also assume Rooker, Larnach, Gordon, and Blankenhorn get some PAs and starts this year. If a catcher goes down it's a toss up between Astudillo getting some spot starts, Rortvedt getting called up, or Telis getting a shot (Astudillo DFA'd then?). But, assuming no long term injuries to Garver or Jeffers, those last 63 starts and 475 PAs are split between Astudillo, Rooker, Larnach, Gordon, and Blankenhorn. 5 guys for 63 starts and 475 PAs.
If (when) Buxton gets hurt they aren't sliding Kepler to CF, putting Cave in one corner opposite Kirilloff and moving Astudillo to the 4th OF spot. Astudillo gets no more ABs because of a Buxton injury. They call up Rooker or Larnach to platoon/compete with Cave. So Astudillo is still not vital to team. And it raises Cave's, Rooker's and/or Larnach's start and PA total, not Astudillo's. If Donaldson goes down Arraez gets plugged in and Blankenhorn or Gordon get called up to serve as 5th IF. So it raises their start and PAs numbers. Same scenarios for any OF or IF injury just with different position changes depending on who goes down.
I know Baldelli likes to get guys rest, but this team is set up differently than the previous ones. They are short on veterans that demand playing time, and they have a handful of young guys on the 40 man who will be the fill ins for the backups if starters go down. But they aren't going to have those young guys sitting on the bench in Minneapolis when they could be getting every day ABs in St Paul (or other minor league locations). Rooker may platoon with Cave early, but that would mean Kirilloff is in the minors and so the 26th man spot is still open. They aren't going to have a young guy getting 1 or 2 starts a week in the bigs. They just aren't. That's terrible player development. And they have 11 guys who they want to get regular ABs (if Garver is 2019 Garver they'll want him getting more than those 375-400 PAs). They can get their regular rest while still having legit MLB starters in there every day. That, mixed with the young guys not sitting on the bench, means they're likely looking for a veteran guy who can be a start every 10 days guy. Astudillo fits that role. When injuries, or poor performance, start popping up things change. But he fits the early season "you're never really going to play cuz we need to get these 11 guys regular ABs" role.