First base:
2018: Mitch Moreland, Hanley Ramirez
2019: Mitch Moreland, Sam Travis
With Steve Pearce beginning the year on the IL, Sam Travis gets a roster spot on Opening Day. However, Mitch Moreland will get the majority of playing time until Pearce returns. Once Pearce does return, Cora has said he will hit third against lefties.
With the Red Sox facing a lefty today in Marco Gonzales, Moreland gets the start. It was a tale of two halves for Moreland, as he posted a .853 OPS in the first half and just .600 in the second. It is unlikely he is the player we saw in the first half, but expecting somewhere in between those two halves for the season is realistic.
Travis was a second-round pick in 2014. Over 121 major league plate appearances, he has a .663 OPS. He will try and show something during this chance he is getting, as he will likely be competing to either be a part of a first base platoon or just be the starting first baseman next season, with Pearce and Moreland both becoming free agents.
Second base:
2018: Eduardo Nunez, Brock Holt
2019: Eduardo Nunez, Brock Holt
Because of Dustin Pedroia‘s lingering injury, there has not been much of a change here. Nunez will be the starter until Pedroia returns, with Holt in his super-utility role. Last year, Nunez was not entirely healthy himself, and his numbers showed it. He had a .677 OPS in what was his worst season since 2014. He also was not as aggressive on the basepaths as he used to be, stealing just 7 bases.
On the other hand, Holt was a very useful bench bat, finishing with a career-best .774 OPS. Beyond these two and Pedroia, the top depth is Tzu-Wei Lin. Lin will begin the year in Pawtucket but will likely be in the majors at some point.
Shortstop:
2018: Xander Bogaerts
2019: Xander Bogaerts
There is not much to say here. Xander Bogaerts is the shortstop and will be for the whole season unless he gets hurt. Bogaerts brings a big bat to the Red Sox lineup and will likely hit 5th for the majority of the year. The depth after him is Tzu-Wei Lin and Mike Miller. With Bogaerts a free agent after this season, those two, and C.J. Chatham are worth keeping an eye on as possible starters in 2020.
Third base:
2018: Rafael Devers
2019: Rafael Devers
Coming into 2018, expectations were high for Rafael Devers after a strong rookie season. He failed to meet these expectations, as his BABIP dropped 61 points, and his numbers showed it. In addition to the massive BABIP drop, health became an issue for the young third baseman. Now, in a new year, the expectations are high again. Alex Cora has said he wants Devers to third hit and he is doing just that on Opening Day. If he breaks out, he could be one of the best bats in the lineup.