The most vulnerable teams are those in the Appalachian League, Northwest League and New York-Penn League . Other short-season teams, like the Brooklyn Cyclones, the Mets’ short-season team in the New York-Penn League , could be converted to full-season teams, perhaps even in higher levels like Class AA.

For some minor league owners, the proposal could mean losing their affiliation with M.L.B. clubs, which gives them cachet and adds value to their investment. O’Conner estimated that only eight to 10 of the proposed 42 teams targeted for restructuring would have the financial wherewithal to sustain the new model. The rest, he said, would wither away.

“If they don’t fold immediately, they would soon go out of business and we would lose baseball in those cities,” he said.

But M.L.B. is committed to a significant change because officials feel that about one-fourth of the minor league teams are not operating at a high-enough standard for modern athletes. M.L.B. also is under pressure to increase player compensation — the league has been sued over that issue — and is looking for a way to increase player wages, perhaps by as much as 50 percent. That is still below a rate sought by the complainants in the lawsuit.

Some M.L.B. teams conclude that the odds of a player selected in the latter rounds of the draft making it to the majors are so slim that it is not worth paying for the development of players who will never help the parent club.

M.L.B is also insisting that some of the minor league clubs upgrade their facilities so that their top prospects are not working in substandard training rooms with poor nutrition programs. Many of minor league facilities do not match the standards of even small college stadiums.

O’Conner conceded that upgrades have been made and more are needed, but he said that some minor league owners do not have the resources to make capitol improvements and that municipalities are reluctant to contribute. M.L.B. has also proposed a revenue-sharing plan — or a tax — in which the more profitable minor league clubs would contribute to the teams in poorer financial health.