The 49ers’ new most outspoken player isn’t happy with one of the NFL’s new rules designed to keep players safe.

All-Pro cornerback Richard Sherman on Sunday went on Twitter following Saturday’s preseason loss to the Texans to voice his displeasure over the new rule that prohibits would-be tacklers from leading with their helmets.

Sherman said trying to take down a ball carrier without leading with the head is “impossible.”

According to the league, the new rule states: “It is a foul if a player lowers his head to initiate and make contact with his helmet against an opponent. This rule pertains to all players on the field, and to all areas of the field.”

The 49ers have been flagged under the new rule three times in two preseason games, including twice in Houston. Both calls on Saturday were controversial.

The first came when gunner Raheem Mostert appeared to make a form tackle of Houston punt returner Tyler Ervin. Most of the contact came between Mostert’s shoulder and Ervin’s chest, though Mostert’s helmet appeared to glance off Ervin’s arm.

Since the rule has been instituted, players have pointed out the difficulty in leading with the shoulder without putting the head down, particularly when trying to tackle a moving target. It’s been the hot-button topic throughout the NFL through the first two weeks of the exhibition season.

The second flag on Saturday came on pass rusher Jeremiah Attoachu, who was penalized for leading with his helmet while using a bull rush against a Texans offensive lineman. Attaochu appeared to initiate contact with his hands before putting his helmet down, making contact and trying to push through the block.

The new rule is not reviewable and requires officials to make split-second decisions when it comes to throwing a flag. And because the new rule is a point of emphasis, officials are encouraged to err on the side of calling a penalty for the sake of players’ safety.

Sherman called for the rule to be “dismissed immediately.” But that seems unlikely given the league’s mandate to emphasize safety.

Perhaps it would be best if the penalties were reviewable in order to take the onus off the officials to make the decision in real time, particularly with the fouls being worth 15 yards.

The league should consider having an official in the replay booth who could make a determination on the fouls after flags are thrown, rather than going to the standard replay review that can take minutes at a time and slow down the pace of play. Creating that type of system shouldn’t be difficult given the amount of cameras and video technology already at the league’s disposal.

Anyone watching the game on television is given slow-motion replays at various angles, which makes it far easier to determine if a play is worth a 15-yard penalty than watching it on the field in real time.

Without a change the process governing the rule, the league is risking this topic becoming a huge part of the upcoming season for the wrong reasons.