3) Jo Adell
This is the year where Jo Adell has to show he belongs. He has yet to do that in his four MLB seasons, but this is a year where the Angels have no choice but to see what he can do. The reason why is the same for the others on this list. He's out of options, and the Angels won't want to lose him.
The issue with Adell being an essential lock on the Angels Opening Day roster is he already won't have a starting spot with how this roster is constructed. The outfield consists of Taylor Ward, Mike Trout, and Mickey Moniak. The DH will presumably be one of Luis Rengifo or Brandon Drury.
There's room for Adell as a fourth outfielder or as a platoon partner for Moniak in right field, but there're a couple of issues here. Young players generally don't excel when their playing time is limited. If the Angels have any hope of Adell blossoming into a regular for them, it'll be hard to see major strides with him playing once or twice a week. When it comes to Adell being Moniak's platoon partner, that sounds good, but he has just a .621 OPS against lefties in his MLB career, and was slightly worse against lefties in the minors.
The Angels have a really tough situation here with Adell. On one hand, they don't want to give up so quickly on a player with this much talent that they drafted in the first round not too long ago. On the other hand, he's not good enough to start, doesn't really have a role that will lead to a lot of playing time without injury, and can't be sent back down to the minors without being DFA'd.
What the Angels end up doing with Adell is anyone's best guess, but it's really hard to see him getting DFA'd before the start of the season. If he's here, he's going to make the team. Considering he hasn't shown much of anything at the MLB level, it's hard to see him sticking the entire year.