For Martinez, such a move mirrors his 2009, when he waited until July to sign with the Phillies. He was effective for them, pitching to a 3.63 ERA in regular-season 44 2/3 innings, along with several strong postseason starts.
Smoltz improved greatly as the 2009 season progressed, faltering badly with Boston but pitching to a 4.26 ERA with St. Louis.
The peripheral numbers for both pitchers suggest that they can help major league teams this season. However, considering that neither one has pitched 200 innings since Smoltz did in 2007, this seems like a wise decision for both of them.