Although Thomas is a raw developmental project unlikely to be ready for another couple of years, Arians didn't want to ruin that potential before the former Virginia Tech star had a fighting chance to stick at quarterback in the NFL.
Arians has been particularly impressed with Sims, who began his college career at Alabama.
"He was able to get it. His reads were correct," Arians gushed after rookie minicamp. "He actually changed a protection once and I was like, 'Whoa, you're up to level five already. These guys can't do that.' And he was very accurate. He got my attention. He's in the mix."
That glowing report on Sims is evidence that Arians has gone from coddling Thomas as a rookie to challenging him as an NFL sophomore.
The latest Around The NFL Podcast welcomes Lindsay Rhodes to discuss the Patriots' response in the "Deflategate" saga and the latest names revealed on the "The Top 100 Players of 2015" countdown. Find more Around The NFL content on NFL NOW.