No more than a handful need to know. Most players don't ask questions about what their team doctors give them. See juve in the 90s etc.
I suspect in this day and age, given the coverage this type of thing gets and the education they've had regarding supplements etc. players are more savvy than they once were and certainly better advised. Especially given the potential penalties for them personally, i.e. a ban and instant dismissal which above all else hits them in the pocket. At top clubs these players could arguably go anywhere so why would they take that risk? The power lies with the players these days and the vast majority will very much know it - there is far less loyalty or ability for a club to put pressure on its players these days. It would take only one disaffected player (or ex-player, or doctor or some other random member of staff) to speak out.
If a manager wanted his side to engage in systematic doping "in house" (which it would have to be, since 25 players visiting the same doctor or clinic regularly would be discovered in no time), it is inconceivable that he could do so without the club's approval to employ that particular doctor and would need the top people in the club involved since logistically there is no other way. The club would need to be aware of him being there, the medical teams would all have to know. The club would (as a corporate entity) need to be involved and therefore, those senior executives would stand not only to lose financially if the club was caught out but would also potentially face criminal sanctions. Would they take that risk for marginal gains in a sport in which physical intensity is important but rarely decisive? Also, any such doctor prepared to do that is likely to have a history of it (or be suspected of it) and any association with a club would be instantly toxic for it.
I just can't see how it could be done, or more importantly why. I've no doubt some players have, or do engage in it to try and give themselves an advantage or make it to the next level but that'll be the case in any sport.