I'm got almost all my VIP and Exec. seats built and a fully upgraded fitness center and training hall. I also have my coaches fully upgraded. Is it worthwhile to upgrade my doctors? It's at 1 now and I haven't had a time when more that one player was ever injured.

Full doctors cost 900k for an entire season.
Full doctors also give an injured player 100% chance to recover 1 additional day and 40% chance to recover 2 additional days during each injury update.
They also reduce the potential of training injuries by 50%

I had my star QB get injured this season for 14 days. I immediately hired full staff and he was only hurt for 6 and thus never missed a training update. Luckily there was no cup match that week and i found a quality back up QB on the transfer wire before the next league game.

I had to pay $1.2 million for that back up QB, that is 1.3 seasons of a full doctor. I think i'm keeping the full doctor for a long time.