Just posted on Fangraphs:
https://blogs.fangraphs.com/slumping-red-sox-get-a-boost-with-the-returns-of-chris-sale-and-kyle-schwarber/
Sale joins a rotation that has been more solid and stable than spectacular. The Red Sox are the only team in the majors with five pitchers who have made at least 20 starts apiece, but both Garrett Richards (5.22 ERA, 5.17 FIP) and Martín Pérez (4.77 ERA, 4.92 FIP) have recently been exiled to the bullpen in favor of rookie Tanner Houck (who has yo-yoed between Triple-A Worcester and Boston but is expected to remain in the majors following Tuesday’s start against the Yankees) and Sale. The unit as a whole ranks a middling eighth in the AL in ERA (4.52) but fourth in FIP (3.92), though in the second half, those numbers have risen to 4.67 and 4.07, respectively. A lack of defensive support — the Sox are dead last in the league in defensive efficiency (.658), 18 points below the 14th-ranked Orioles and 35 points below league average — has contributed to the ERA/FIP gap. Of the five regular starters, only Nick Pivetta has a BABIP below .325, and both Nathan Eovaldi and Eduardo Rodriguez have ERAs more than a run above their FIPs. While the Sox aren’t likely to push either Sale or the 25-year-old Houck too hard, the hope is that they can at least pitch deeper into ballgames than the pair they replaced, who by combining to average less than five innings per turn taxed a bullpen that’s been hit for a 4.93 ERA and 4.14 ERA since the All-Star break.