"I'm a little disappointed with where Coop is at right now," Arians said, per the team's official website. "I'd hope he come a little faster."
The coach admitted that some of the guard's struggles are due to rustiness but added that backup Earl Watford, a 2013 fourth-round pick, has been pushing Cooper for playing time.
"To get back into the speed of the game, he needs to pick it up," Arians said, per KGME-AM's Mike Jurecki. "We need to see that special player we drafted last year."