San Francisco 49ers cornerback Richard Sherman has a lot to say about the NFL’s new helmet, none of it good.

Sherman voiced his frustration via Twitter Sunday following his team’s 16-13 preseason loss to the Houston Texans.

“To all those ppl including those who made the rule, I want a video of YOU running full speed and being lead by anything but your head while also attempting to bring down a moving target. You will soon realize it’s impossible,” Sherman wrote, according to Bleacher Report. A video of of a tackle from teammate Raheem Mostert that drew a penalty flag and a video of a rugby tackle, which Sherman noted would be penalized in the NFL, reportedly accompanied the tweet.

“There is no ‘make adjustment’ to the way you tackle,” Sherman continued. “Even in a perfect form tackle, the body is led by the head. The rule is idiotic and should be dismissed immediately. When you watch rugby players tackle they are still lead by their head. Will be flag football soon.”

The rule change reportedly calls for a penalty whenever an offensive or defensive player “initiates contact with his helmet to any part of an opposing player’s body.” It was approved in March and could result in an ejection if the penalty is deemed particularly severe.

According to Mike Florio of Pro Football Talk, the NFL secretly slipped the new helmet rule onto the agenda of Competition Committee proposals in March”in an attempt address the “leading with the helmet” controversy. Florio says any change  to the rule would require the approval of at least 24 of the league’s 32 owners.