Do MLB Players know who are using PEDs?

According to the NY DAILY NEWS some are 50/50 on who the players thing are.

This is from Mark Teixiera about Robinson Cano.

Read more here.

I wonder how many players figure out who does and doesn't do them. Do the ones not doing them get pissed off at the ones that are and do they tip off the MLB? Do they toe the line with the MLBPA and just go with it because the better a superstar plays the better the contracts end up getting for all the other players?