With no designated hitter for the three games in St. Louis, the lineup change allowed Napoli to start for the second day in a row instead of sitting twice in three days.
Boston gets the DH back on Friday for the start of a three-game series in Anaheim.
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.