How badly did the Red Sox batter the Yankees' pitchers this season? Well, the Yankees' ERA against Boston this year was the worst ever. The Yankees' ERA of 6.19 tops the 1959's staff's 6.17.
In recent years, the 2005 Yankees were beaten up for a 5.80 ERA. In 1988, it was 5.79 and in 1948, it was 5.63.
According to StatsPass, the Yankees allowed a .503 slugging percentage to the Red Sox this season, which is the highest since 1921. The Sox's batting average (.315) and OBP (.383) are the 2nd-highest since 1921.
(H/T to ESPN Stats & Info.)