According to ESPN‘s Adam Rubin, Sandy Alderson “all but acknowledged” that the Opening Day payroll will be lower than it is at this point in the offseason.
Currently, the payroll is estimated to be around $150 million. Once the Mets trade Jay Bruce ($13M) or Curtis Granderson ($15M), that payroll will shrink by an amount dependent on who the Mets get in return.
Those huge contracts probably will not be completely reinvested in the bullpen, ruling out an expensive reliever such as David Robertson (2 years, $25M remaining).
You can expect one or two solid, cheaper additions to the bullpen in the near future, whether it be in a trade with the Rangers or someone else.