Monday morning WSJ:
Now baseball is trying to settle the debate once and for all. On Tuesday, MLB will launch a pilot program in the minor leagues of a replay system for check swings, the term used to describe when a hitter begins to swing but then stops partway through. The test, which will take place in the Single-A Florida State League, is an effort to inject a degree of objectivity into the murkiest calls umpires have to make.
The new rule will work similarly to the automated strike zone that was auditioned during spring training this year and uses the same technology. Teams will have the ability to ask a computer to determine whether a hitter swung or not. If the head of the bat is ahead of the knob on the end by more than 45 degrees, the pitch will be deemed a strike.
Check Check
MLB will start testing a challenge system for checking a swing. If the head of the bat is ahead of the knob by more than 45 degrees it will be considered a swing.
Source: MLB
Brian McGill/WSJ
League officials caution that the system—which was briefly introduced last year in the Arizona Fall League—remains a work in progress. It is still far too soon to begin to contemplate when or if a version of it will ever come to the majors.