In a text message sent to Jastremski, McNally referred to himself as the "deflator." Yet, according to the Patriots, there's a simple explanation for McNally's nickname. They claim it has nothing to do with deflating footballs, and instead, they claim it has everything to do with McNally wanting to lose weight.
Mr. Jastremski would sometimes work out and bulk up -- he is a slender guy and his goal was to get to 200 pounds. Mr. McNally is a big fellow and had the opposite goal: to lose weight. "Deflate" was a term they used to refer to losing weight. One can specifically see this use of the term in a Nov. 30, 2014 text from Mr. McNally to Mr. Jastremski: "deflate and give somebody that jacket." (p. 87). This banter, and Mr. McNally's goal of losing weight, meant Mr. McNally was the "deflator." There was nothing complicated or sinister about it.