A universal designated hitter - something the players have sought for more than three decades, according to commissioner Rob Manfred - also was part of the union's proposal.
A 20-second pitch clock.
Major League Baseball and the players' association continue to discuss possible amendments to the usage of the list itself, as a number of teams have been accused of using a shorter DL - it was changed from 15 days to 10 days in 2017 - to manipulate their rosters, sources told ESPN.
However, the negotiation reportedly includes forcing relief pitchers to face a minimum of three batters. Also on the list of rules under consideration is moving away from multiple trade deadlines - now there is a non-waiver deadline in July, plus the waivers-required date a month later. The union has expressed interest in 15 days for pitchers - who are typically the subject of roster manipulation - and 10 days for position players.
A reduction in mound visits from six to five.
A rule that would permit two-sport athletes, such as Kyler Murray, to sign major league contracts as enticement to play baseball.
Major rule changes could be coming to Major League Baseball as soon as the upcoming season. However, the three-batter minimum and 12-pitcher maximum would make left-handed specialists in the bullpen harder to keep on the roster. Owners and other high-ranking team officials at the meetings will be updated on the status of those talks during Friday's general session. The union has also seen the issue of "tanking" - teams stripping its payroll and hoarding prospects and draft picks - as a fundamental problem.
Of all the proposed changes, the universal DH arguably would be the most significant to the game on the field. It is customary under present rules for managers to use a relief pitcher for one out, even if that at-bat requires just one pitch.