Earlier today, the Mets called up top prospect Michael Conforto. The outfielder hadn't previously been on the team's 40-man roster, but the Mets have cleared a spot for him there by shifting right-handed pitcher Rafael Montero fro the 15-day to the 60-day disabled list. The move is purely procedural, as Montero has been on the disabled list for well over sixty days, and unlike players on the 15-day disabled list, players on the 60-day disabled list are excluded from the count of players on the 40-man roster.
Shut down early in the year with shoulder soreness, Montero pitched a few games for the Mets in April. He made four relief appearances early before the team sent him down to Vegas for a couple of outings and called him up for a spot start on April 28. He was shut down after that appearance and did not pitch again until he resurfaced with the Gulf Coast League Mets on July 14. He threw one scoreless inning that day and three more scoreless innings on July 20.
The Mets still have some flexibility on the 40-man roster if they need to add players to it in the near term. David Wright is still on the 15-day disabled list and could be shifted like Montero was today. The same could be said for Erik Goeddel, whose return is likely to come more than sixty days after he was placed on the disabled list. And, of course, players like Dario Alvarez, Akeel Morris, and Wilfredo Tovar—minor leaguers who probably won't play for the Mets much, if at all, this year—could be designated for assignment to make room in the event that everyone ends up healthy at the same time.