Starting pitchers:
Before the season, the rotation looked like it would be an extremely strong part of the Red Sox team. 2 months in, however, they have struggled. Nathan Eovaldi is hurt, while Rick Porcello and Eduardo Rodriguez have struggled. This has left the Red Sox with just two reliable starters, David Price, and Chris Sale, who also had his struggles early on.
Madison Bumgarner:
In 2014, Madison Bumgarner, put together one of the most dominant postseasons in history, leading the Giants to their 3rd title in 5 years. Fast forward 5 years and the Giants are no longer the contenders they once were while he is in the final year of his deal.
While he is not the ace he once was, he is still an effective pitcher with an extraordinary postseason track record. He has a 3.83 ERA and a 3.88 FIP. He would certainly be a good add for a postseason push to a currently thin rotation.
Tanner Roark:
In his first year with Cincinnati, Tanner Roark has had a bit of a resurgence following 2 lesser years in Washington. He currently has a 3.74 ERA with a 3.44 FIP. His pitch usage has changed this year, as he is throwing fastball less and his slider much more.
This may have something to do with the bounce back. He could be a solid back end starter but not really much more than this.
Zack Wheeler:
After dealing with injuries for years, Zack Wheeler finally was able to get back on the mound for good in 2018 and was phenomenal. While his ERA this season at 4.87 does not look good, his 3.73 FIP points to signs that he will have some nice improvements soon.
He could be a 3 or better and this also depends on whether or not the Mets make him available, considering they could be a threat in the NL East.