Nationals manager Dave Martinez accused Reds 3B Elly De La Cruz of an illegal bat prior to his first plate appearance of the game, spurring Crew Chief Adrian Johnson's call to Replay HQ and HP Umpire Quinn Wolcott's order to remove a data capture tool on the knob of the bat. De La Cruz got the last laugh, hitting a home run several innings later...while using the same bat with the knob cap back in place.
Although Official Baseball Rule 3.02 describes a legal bat (and what alterations potentially could make it illegal), OBR 6.03(a)(5) concerning batter illegal action is the meat of the illegal bat issue.
It delineates what exactly makes a bat illegal—namely, that it has been "altered or tampered with in such a way to improve the distance factor or cause an unusual reaction on the baseball. This includes bats that are filled, flat-surfaced, nailed, hollowed, grooved or covered with a substance such as paraffin, wax."
This rule imposes a penalty of declaring the batter out for the illegal bat, removing the bat from the game, and ejecting the player to boot, where the Commissioner's Office may then opt to impose additional penalties, fines, and suspensions.
OBR 6.03(a)(5) MLBUM interpretation lays out the policies for illegal bat inspections: "Each manager is limited to making this request one time per game." Thus, Davey's 2nd inning request precluded him from making another request in the 5th inning when De La Cruz returned to home plate with the data device once again on the bat.
Lindsay's Call: Finally, my issue with this entire episode is the same issue I have with managers requesting substance inspections or equipment inspections of opposing pitchers: if the manager is wrong, there is no penalty for the failed request. I would prefer MLB took a page from the NHL and adopt a failed challenge penalty akin to hockey's rule regarding failed illegal stick challenges: "If the complaint is not sustained, a bench minor penalty shall be imposed against the complaining Club."
Baseball obviously has no such "minor penalty," but that's what Rules Committee is for...
Video as follows: