Ted Williams and many other Hall of Famers never won a World Series. Herb Washington, a bizarre (and ultimately unsuccessful) experimental “designated runner”, did, although he was partially responsible for the A’s only loss in that series by getting picked off at first in the ninth inning.
The largest group of less-than-ideal champion players are simply bench/low-level players who just happened to be on a championship team. Little needs to be said about them except that they got lucky in that circumstance. (Robert Horry is perhaps the king of these players-he managed to win more championships than Michael Jordan while being only a decent journeyman stats-wise.)
Then there are the players in starring roles who, while not absolute flops, are still less than ideal. The king of these players is Trent Dilfer, the man who won a Super Bowl thanks to his team’s defense and then got cut. “Honorable” mentions include all the starting centers on the Bulls and Warriors dynasties and many of the pitchers on the 1920s Yankees.