2019 – Commissioner Rob Manfred announces rule changes for the coming season. While the idea of a pitch clock has been dropped, other measures adopted include: lowering the number of mound visits from six to five, following the successful introduction of the rule in 2018; a shorter break between innings; making the July 31st trading deadline a hard one, with no trades allowed for the two remaining months of the season; a shift in procedure for nominating starters in the All-Star Game and additional bonuses for participants in the Home Run Derby; beginning next season, a clear roster limit, with 26 during the first five months and 28 for September, with all teams being required to respect the limits; and a minimum of three batters faced for relief pitchers, barring injury or the end of the half-inning, also starting with the 2020 season.

On March 14, — 2019 – Commissioner Rob Manfred announces rule changes for the coming season. While the idea of a pitch clock has been dropped, other measures adopted include: lowering the number of mound visits from six to five, following the successful introduction of the rule in 2018; a shorter break between innings; making the July 31st trading deadline a hard one, with no trades allowed for the two remaining months of the season; a shift in procedure for nominating starters in the All-Star Game and additional bonuses for participants in the Home Run Derby; beginning next season, a clear roster limit, with 26 during the first five months and 28 for September, with all teams being required to respect the limits; and a minimum of three batters faced for relief pitchers, barring injury or the end of the half-inning, also starting with the 2020 season.

Sources –
Baseball Reference March 14
SABR Games Project
National Pastime March 14
Retro Sheet
Replay The Game