Personally, when I competed myself - I had plenty of strains and tears (not a muscle tears, but ligaments). If I am correct (medical and sport related medical terminology differ, especially in Europe and USA), lesser grade - lesser damage. As with god forbid cancer. From 1 to 4. Still, a muscle strain, especially for a such big muscle as hamstring, it is impossible to get back to a 100% with massages, different types of treatments (heating up affected and surrounding areas with electromagnetic feels, electro stimulation, heating mud, salt baths, injecting Vitamin B complexes plus Magnesium and Potassium and over needed mineral elements. In my times it was no less than 2 weeks of intense therapy. Nowadays sports medicine is on a space technology level, but requirements for the NBA pro athlete are on the space level too. I hope that 2 weeks or even a bit less should fix Domas.
To summarize: grade 1 level muscle strain is a lite scare. More severe strain or even the horror of a muscle tear (even it's just a small one) - oh boy. Hamstring muscles sit in a capsules that end up transforming into ligaments that connects to the parts of the bones or joints and have to work as whole unit. Grade 1 strain? OK, 2 weeks and Domas will start again.