As the calendar turns to May, there has been enough baseball played that every team should be, at a minimum, re-evaluating their "Plan A," if they hadn't been already. Are you daydreaming about trades for Mike Trout? Keep dreaming. Until teams become serious sellers later in the summer, most upgrades have to come from within, either using different players or using the existing talent in a different manner.
With our heads firmly in reality, what moves can teams actually make to improve in the short term? For all but a few of the 30 suggested changes (which I'll note), the ZiPS projection system estimates a rest-of-season improvement of at least five net runs, or about half a win.
American League East
While I appreciate the creativity to use a player like Seth Smith at leadoff, Hyun Soo Kim was the team's OBP leader in 2016, projected to be the leader again in 2017, and the team has hit him mostly seventh in the lineup. In addition, I still think the team gave up way too soon on Kim hitting left-handed pitchers; he actually had fairly normal platoon splits for a left-handed batter in Korea. Generic platoon splits for all players predict a specific player's future platoon splits far better than his actual platoon splits until you're talking 2,000 to 3,000 career plate appearances.
The projections never completely bought into Sandy Leon's 2016, and it's hard to say, at least so far, that the projections have been wrong. Still, ZiPS projects Christian Vazquez as only a little better than Leon the rest of the way. And as poor a start as he has had, none of the Red Sox minor league options look to be a significant upgrade over Steven Wright.
You can't get a five-run move here unless the Red Sox can get David Ortiz to come out of retirement.