Masi served as the Braves' backup catcher first to Al López, then Ray Berres, and finally to Ernie Lombardi. He began to develop his reputation as a good defensive catcher from his association with knuckleball pitcher Jim Tobin. The other Braves catchers shunned Tobin due to the unpredictability of the notoriously difficult to catch knuckleball and, Masi took over the job as his catcher. When Lombardi was traded to the New York Giants in 1943, Masi became the Braves regular catcher. His work with Tobin paid off on April 27, 1944 when Tobin pitched a no hitter against the Brooklyn Dodgers.