Learn Turkish: Ekibin incelediği çizelge çok eski olsa gerek. - The schedule that the team examined must be very old.

This is a set structure for making a strong logical deduction. By taking a verb or adjective (here, eski combined with the helper verb olmak), adding the conditional -sa, and finishing with gerek (necessary), you express a strong assumption: "it must be old" or "it is necessarily old."

Could we just say çok eski olmalı instead of çok eski olsa gerek?

Yes, çok eski olmalı also translates to "it must be very old." However, olsa gerek is often preferred for logical deductions and assumptions based on evidence. While -mAlI can sometimes blur the line between deduction and obligation, olsa gerek is purely for deduction and sounds a bit more analytical.

Why does ekip (team) take the genitive suffix -in to become ekibin?

This happens because of the object participle incelediği (which they examined). In Turkish relative clauses where the subject of the clause (the team) is different from the noun being described (the schedule), the subject takes the genitive case (ekibin) and the participle takes a possessive suffix (-i). It literally acts like "the team's examined schedule."

How do we know if incelediği means the schedule they examined (past) or are examining (present)?