It's more than four hitters, but according to the data on bb-ref, there are four Red Sox starting position players providing sub-.600 OPS: C, 2B, SS, 3B. Not even Red can argue with those stats.
Some of those "starters" have been replaced lately by the likes of IKF, Gasper, and Andruw Movinginstero. But even those guys are still sub-.700. And so is the DH/LF spot, whether manned by Anthony, Yoshida or the wildly inconsistent Duran.
The team's OPS is sub-.700. But it's a thousand degrees outside, so maybe Sam's "embarrassing and unacceptable" roster will heat up like he once predicted...
... before he said this week, "Let's be honest- " (when people say that, are they admitting they weren't before?) "... we may have to pivot."