Neither a one month sample. Or 2 or 3. Look at Barnes.
Robles was a disaster when he arrived to Boston and you don't need stats to figure out. Most people wanted him and his pal from Pittsburgh gone. Robles has improved a lot recently no doubt, and hopefully he keeps that way. Geez I guess he has even earned the closer job for now.
Also, career numbers in fairly large samples are not meaningless even for relievers. Robles is the definition of inconsistency when you look back at his career.
Quoting Forest Gump "He is a box of chocolates, you don't know what you are going to get".
A700's concerns regarding Robles are 100% valid.