I've never tried that, but I wouldn't. Mail doesn't always get distributed immediately, so you might miss the player you're looking for. I'd just send to their home field

I have sent many items TTM to players in care of their team, but can you send something to be signed to the opposing team as well. For example, if I know the Atlanta Braves are going to play in Oakland next week and I send a card to Jason Heyward of Atlanta to the Oakland Stadium, will they give it to him? Thanks for any input on this matter.