Antonio Brown filed a second grievance with the NFL on Monday in his fight to wear his preferred helmet, though it didn't prevent him from practicing with the Oakland Raiders on Tuesday.

"It's a certified helmet," head coach Jon Gruden told reporters regarding the helmet Brown wore during that practice, per Scott Bair of NBC Sports Bay Area.

"He's all-in. Ready to go," Gruden added, according to Vic Tafur of The Athletic, noting he doesn't believe Brown's feet issues are a concern at this point.

Brown has missed time in training camp because of his feet and also left camp when he filed his first grievance against the NFL, a dispute he lost. In essence, Brown was told he couldn't wear his preferred Schutt AiR Advantage helmet because it was over 10 years old, and no helmet that old would be approved by the National Operating Committee on Standards for Athletic Equipment.

But Brown found models of the Schutt AiR Advantage that were less than 10 years old and petitioned the NFL with the hope that a loophole might grant him one more season with his helmet of choice, as Pro Football Talk's Mike Florio wrote:

"Because the Schutt AiR Advantage hasn't been banned generally by the NFL, he should be permitted to wear one that is less than 10 years old, and that can be recertified by NOCSAE.

"The NFL did not include the Schutt AiR Advantage within the list of 11 helmet models banned in 2018. The NFL also gave players wearing banned helmets a one-year grace period, allowing them to continue to wear the banned helmet while transitioning to a new model.

"Brown hasn't received that courtesy, because the NFL didn't ban the Schutt AiR Advantage until he found multiple models that were less than 10 years old, and thus that could be recertified by NOCSAE."

It was unclear if Brown would leave training camp again because of this new grievance. What was clear was that general manager Mike Mayock and the Raiders were running thin on patience with their star wideout:

Brown apparently took those words to heart, appearing at training camp this week. And the fact that he practiced with a certified helmet is a good indication he'll remain with the team going forward, whether he wins this latest grievance or not.