Remember Travis Shaw, the star sent to Milwaukee in the Tyler Thornburg trade? After two stellar 2017 and 2018 seasons, he was ineffective in his 2019 campaign. While Shaw is a third baseman, he could play first in a return to Boston.
He could be a more appealing option than Cron since Shaw hits left-handed. This means he could platoon nicely with Dalbec because they would be a lefty-righty combo, similar to the 2018/2019 duo of Moreland/Pearce.
Shaw is also 29 years old which means he is in the midst of his prime. He has had two star-caliber seasons (121 and 119 OPS+ in 2017 and 2018) and he can lengthen out the Red Sox lineup. A one or two-year deal could be wondrous for Boston. If he can find his previous form, he can be a force for Boston at a relatively cheap price.
Shaw may want to hit the free agent market next year as the third base class will be significantly weaker. Anthony Rendon, Josh Donaldson, and Mike Moustakas (who recently signed with the Reds) dominate the third base class of 2019.
If Shaw is willing to take a one-year deal, Chaim Bloom should jump all over that. Familiar with Boston as he played for them from 2015 and 2016, the Red Sox and the third baseman could reunite for the 2020 season.