To give you some hope, I work with a horse who completely severed a hind superficial digital flexor tendon as a 12 year old, and continued to work until he was around twenty. However, his owners sent him to the best vet hospital in the south west of the UK, and spent thousands of pounds on his treatment. He was then confined to cross ties on a heeled shoe for three months, on a drip, then another year was spent on box rest.
No life for a horse, in my opinion.
Like I said, he went on to work as a happy hacking horse for around 7 years after that, but has always had a "bowed tendon" look to that leg, and he has had to occasionally wear shoes like this behind if it's been bothering him:
Now, if he had been mine, it sounds awful but I would have potentially put him to sleep - not leaving a stall for a year is pretty much cruel to an animal like a horse, in my opinion. He is now 22, and retired due to him being just a bit stiff and an old man.
Now, as yours isn't a compete tear, it may carry a better prognosis, I don't know.
Here's a picture of Vic when he was still in work, the handsome devil. You can see the bow in the near hind tendon if you look closely.