Montgomery (elbow) threw about 50 or 60 times off flat ground Saturday, Bryan Hoch of MLB.com reports.
Montgomery is expected to gradually increase the distance he plays catch over the next week or so before progressing to mound work. The lefty has been sidelined since May 1 with an elbow strain and will likely require at least two rehab starts before being activated from the 10-day disabled list, so it's not expected that he'll be an option for the Yankees rotation until mid-to-late June at the soonest. His ongoing absence will continue to afford more starting opportunities to rookie Domingo German.