Misleading post from Speier.
While the Sox have never gone to the postseason after starting 1-5, bear in mind that stat covers numerous postseason format changes that can affect that outcome. For example, the 1996 Red Sox started out 1-5 (actually 0-5) and did miss the postseason. But they also finished with a record of 85-77 that would have tied them with the White Sox for the third wild card under the current postseason format. (The Sox went 6-6 against each other that year; I’m not digging any deeper into tie breaking rules from 30 years ago.)
I’m sure if I kept looking into it, I could find another season with a 1-5 start where the Sox finished with over 90 wins, but “failed to make the postseason” because only one team from each league made it that year (meaning prior to 1969) or they finished second in the AL East but there were no wild cards (1970 to 1995).
Speier’s statement is very likely true, but not necessarily any sort of harbinger of doom…