Isn't the number of treatments needed for injuries capped at 15? For instance I had a player get a 6 day injury earlier and beyond 4 or 5 days clicking to heal more didn't add more treatments, it just stopped increasing at 15. If this still works for super long injuries like that you may want to try that to get him back right away.

Of course, since he was in a slump, maybe giving him that whole time to recover could get him back on form (but at the cost of a lot of possible training time).

More on topic, I've had a few players that have been slowly sliding into slumps. My GK was constantly at 7-8 every game for the first 15 games I had him, but since he's dropped to nothing but 5-6. It seems like there are a lot of variables related to form.

Moving players slightly can increase it or decrease it. Usually playing in the same position or formation constantly increases it, etc. I'm having trouble with trying to get a few of my players out of their slumps. With offensive or midfielders it seems fairly easy, get them some goals or multiple assists for multiple games in a row, and they're suddenly good again. Defenders it's a bit more difficult, and that's what I'm struggling on now.

I hope you have better luck than I'm having.