When Major League Baseball and MLB Players Association officials meet this week to discuss possible rules changes for the 2018 season, a pitch clock and limitations on mound visits are expected to be the two primary topics, sources have told MLB.com. MLB hasn't officially commented on the meetings.Commissioner Rob Manfred

When Major League Baseball and MLB Players Association officials meet this week to discuss possible rules changes for the 2018 season, a pitch clock and limitations on mound visits are expected to be the two primary topics, sources have told MLB.com. MLB hasn't officially commented on the meetings.

Commissioner Rob Manfred has consistently voiced public support for both measures in order to address concerns about the pace of play. Last year's average game time of three hours, five minutes was the highest in MLB history. In interviews, MLB officials have said they are trying to reduce the amount of down time that occurs during games.

One source within the industry said rules changes of some kind are likely to occur for this season.

ESPN's Jerry Crasnick was first to report that the meetings would occur in New York this week.

While the amount of time for MLB's proposed pitch clock is unclear, a prototype exists with Minor League Baseball's 20-second limit; the Minor League version begins when a pitcher takes possession of the ball on the dirt area around the rubber and ends when the pitcher begins his windup or arrives at the set position.

Under current Minor League rules, the 20-second clock resets whenever a pitcher disengages from the rubber with runners on base or fakes a pickoff throw.

Last offseason, MLB proposed a limit of one mound visit by a catcher per pitcher, per inning, as first reported by USA Today. The MLBPA raised concerns, including the risk of cross-ups between pitchers and catchers. Many mound visits occur because catchers feel compelled to change signs to prevent baserunners from relaying signs to hitters; without those conversations, the MLBPA has suggested confusion could put catchers -- and umpires -- at increased risk of being hit by pitches.

The Commissioner said last February that during the 2016-17 offseason the MLBPA declined to accept MLB's proposals regarding the pitch clock and mound visits. Baseball's Collective Bargaining Agreement permits MLB to impose on-field rule changes unilaterally when at least one year of notice is given to the union. MLB initiated that process in early 2017, and Manfred consistently has said MLB prefers to make changes with MLBPA cooperation.

After the union rejected MLB's broader pace-of-play proposal last year, one notable rules change for 2017 was the institution of automatic intentional walks -- a move that league officials did not expect to substantially affect the average time of games.

League officials sought feedback from active players during the 2017 season in an effort to guide the formation of what MLB hopes will be an acceptable proposal this year. At the very least, MLB owners will get a substantive update on possible rules changes at the quarterly Owners Meetings at the end of this month; presumably, owners could vote on approval by then.

MLB officials previously discussed the possibility of raising the strike zone to the top of the kneecap, but that does not appear to be under serious consideration at the moment.