Mets manager Carlos Mendoza said Tuesday that Martinez is dealing with tightness in his lower back and received an injection for the injury, Will Sammon of The Athletic reports.
Mendoza added that Martinez will be sidelined for up to five days, and he'll continue to ramp up his progress in the minors before joining the team. Martinez played two games at Single-A St. Lucie this past weekend and went 1-for-8 with two walks. He hasn't participated in baseball activities since then due to the back issues.