Every season, teams rely on a few under the radar players to fill in spots and contribute. For the Red Sox last year, it was Ryan Brasier. In 2017, it was Joe Kelly.
With the Red Sox current huge payroll, they cannot afford to bring in top free agents to fill holes. They will likely sign one cheap reliever and possibly make a trade elsewhere and call it an off-season. How much can you really do after a 108 win season and a World Series?
Luckily for the Red Sox, they do have some depth in positions of need, like relief pitcher.