[MikeS369]

When you go into your pregame screen select the Lineup and Starting Pitcher tab.

Replace Ohtani in the pitching section with another pitcher.

Drag Ohtani on the batter lineup part of the page into his batting spot in the lineup. Set him as DH.

Drag Ohtani in the pitcher section back into the starting pitcher slot.

The above does not always work. If it fails, do this.

Cancel the game.

Go to "Pitching" tab. Change the days starting pitcher to someone other than Ohtani.

Go to the pregame screen.

Select Lineup and Starting Pitcher tab.

Drag Ohtani from the Pitchers section to the starting pitcher slot.

Check your batting lineup and make sure Ohtani is listed.

I'm fairly certain if you sim games the AI does not do this so it is best to set Ohtani to "Skip DH when Pitching" on his strategy page.