On Foster - yeah, even putting that out there privately probably isn't too smart. Be careful who you trust folks - most of us have learned that there are very few people you can rely on to have a truly private conversation with. Honestly - given what a lot of idiotic and rude fans have said 'publicly' to Foster on social media, he'd be justified to say whatever he wanted. I've never seen a pro athlete take so much nasty shit from fans. I'll never understand why fans think they have the right to do what they do to players. There's just really no excuse for it, but hey, this is America 2018, right?
On Alex... I don't know anything - and frankly, he has a right to privacy. He could probably sue individuals and some media types for accessing and/or sharing his private health information. However, speculating here, what typically happens when you get a post-op ortho infection is that the hardware put in during the original surgery has to be removed. Sometimes they'll put in temporary 'spacers' to stabilize the extremity, and sometimes they'll remove the hardware and leave it out. They rinse the wound copiously in the OR with antibiotic solution, and obviously put you on hardcore IV antibiotics for several weeks at a minimum. Although MRSA is a possibility, it's not necessarily the only infection that occurs. Sometimes, an infection can be bad enough that some tissue dies and they may have to perform an 'I&D' (incision and drainage) where they open the wound, surgically remove or 'debride' the tissue, and clean out the wound. This can be required several times. They may also have a wound vac in place which is a sterile dressing with special sponges that are packed into the wound with continuous suction applied via a pump which aids greatly in tissue healing.
Those are the kinds of things most likely going on if he has had setbacks/complications as is being (irresponsibly) reported.