I would say I'd be somewhat surprised if Reyes makes it back to Boston, but there really isn't a lot on the 40 to bring another lefty in, assuming they want Okie to get things figured out (if he can) at Pawtucket.
Doubront is getting close, but he'll be starting off in Pawtucket to make up for his lost spring time, and that leaves Miller, Rich Hill, and Randy Williams, all who, like Reyes, are out of options.
Hill and (especially) Miller have the makings of more useful arms than a garden variety LHP out of the pen, so that leaves Williams, who is likely no better or worse than Reyes.
Not sure if designating Reyes to bring in another can kicker is a great move.