Dockett, who is out for the season with a torn ACL, used a dry erase board to write "Worst Team in NFL" and "0-6" and held it up to Raiders fans during the Cardinals' 24-13 win in Oakland.
"It won't happen again," said Arians, of Dockett making the sign.
After the game, Dockett explained the sign on Twitter, saying he wrote it because Raiders fans threw "coins and ice" at the Cardinals and called them "every name in the book."
Arizona (5-1) hosts the Philadelphia Eagles (5-1) on Sunday.
- Molly Geary