that is a abnormally high amount of injuries. i've had 5 in the past 2 seasons combined. and they all were in a 9 week period. none of the injuries were longer than 14 days. i have a fitness hall, but no doctors.

So does the fitness centre.

From FAQ:-

What do I get if I build a fitness centre?
When the fitness center is built, your players get additional 10% on their fitness training points (this works only when training fitness of course). The first upgrade raises this percentage to 15% and the second to 20%. The upgrades also improve the rehabilitation times for your injured players. The first upgrade gives your player 25% more chance every day to skip 2 days towards the full recovery, instead of just 1. The second upgrade raises that chance to 40%.

All I have is a fitness centre, so I normally see 3 days rehab from 2 normal days. Found this works for my economic situation.

Teams with full fitness centre and full doctors seem to get 5 days rehab from 2 normal days.

Docters:-
Your doctors give an injured player 5% (100%) chance to recover 1 additional day and 2% (40%) chance to recover 2 additional days during each injury update.
They also reduce the potential of training injuries by 2% (40%)

The percentasges in brackets are what you recieve paying $45K a week for 20 doctors. So you'll always get the extra day rehab, and 40% chance for another. And you still have the 40% chance from the fitness centre for another day also.

no fitness centre + no docotrs = recover 1 day per day.
fitness centre + no doctors = recover 1-2 days per day.
fitness centre + 20 doctors - recover 2-4 days per day.