I'm not buying the "questions about his commitment to rehab," either, but I'm also not sure it's not an issue.
His injury is not minor, and despite the lies about his being his pinky finger to add effect to the notion he's milking the injury, pain is different for different people and "pain threshold" is not some uniform measuring stick for every injury and future possible injury.
Swing a bat with a ring finger in pain is hard to "put out of your mind" or "just get over it and play through pain."
I'm not sure if Mayer's issue is pain threshold, either or just the proclivity to get hurt doing normal baseball things that hardly anyone else gets hurt doing. I worry much more about him.
I don't think anyone felt there was an issue with Anthony, last season, despite missing the second half, so basically, it is just this one injury that has caused people to jump to the conclusion that he might be fragile,