Rest and the 3 day outlook schedule

Question: One of the things that happens to me more often then I would like is that I have players who need rest, so I will look at the 3 day outlook schedule to see if my team is facing a LHP or RHP and change that lineup accordingly.
But after that game Sims it turns out a different pitcher started for my opponent and my rest doesn't happen and now I have even more players that need rest.
I realize that one possibility is my opponent updated his rotation but it happens far to often for that. I also realize I could just change both lineups, but why should that need to be the answer? Any insight about why this happens so often and what I could do about it is appreciated.

First off -the SIM will always display the Probable Starting Pitcher for both teams - usually teams only have 5 SP and it's a no brainer because everyone else is tired. BUT that can be affected by a few variables

1) Injured Pitcher comes off DL and replaces the Spot starter,
2) Opponent has options and decides to use a Righty SP instead of a Lefty - or vice versa

That's really about it, and IF your opponent has the option to switch his SP to one that throws from the opposite side, it's doubtful they are TRYING to get your guys needing Rest, More like getting their injured guy back!!

One last thing to consider is possibly using the guy you DH all the time in the Field occasionally to rest your other guys by playing them a game at DH -

If you play in Leagues that use Endurance you need to be agile and make the DH day's matter, better to have a lousy fielding 1B for a Game, than having to sit Cecil Fielder against a Lefty in a Big Boost park....

Also, if your league has double headers, the Sim hasn’t figured out how to accurately show which pitcher will pitch the second game of the double header. It doesn’t account for the first game being like a day of rest, so it will often display the wrong pitcher. But a better pitcher will often start game 2 after receiving credit for a day off on the first game.

Also if all SPs are tired/injured and none are rested for the next game, it will start the most rested one but that wont reflect properly on the schedule (which shows the top pitcher in rotation). Everything people mentioned are pretty rare so I cant imagine it happens often.

Thank you for the feedback.
I do use the DH already as you suggest Sincity, but thanks for offering that.
I think what I'm learning is I can't take these schedules word for it, I'm gonna need to check my opponents roster and lineup setting to see if I see anything that could indicate what I see in the schedule may not happen.

I am unsure if the SIM will still display a SP that is Injured but set in your rotation as a Probable Starter when it would be his turn.

The SIM does still show your teams SET lineups but does not account for the fact a player is injured