"This guy is really deeply, deeply competitive," Grigson said. "But at the same time he knows how to stay on a level where all his teammates can identify with him, which is special."
Colts safety Tom Zbikowski, who has gone against Luck every day in practice, says Luck has plenty of arm.
"You watch him make a throw, it looks effortless," Zbikowski said. "Then you watch it on film, it's a laser. You think you have good coverage, and next thing you know it's right where you are not and with a lot more velocity than you think his throwing motion could generate. It looks smooth and effortless."
His arm strength won't matter if Luck does not know where to go with the football. Arians said Luck has been exceptional in picking up the Colts offense, and he said he won't have to scale back anything because of Luck.
But there is a lot to pick up. Luck said learning different words for plays has been challenging. Arians said learning all of the Colts' protections — about 14 of them — has taken a lot of effort from Luck.
Even if Luck does everything right, he still might struggle if the rest of his team does not come together. The difference between Andy Dalton's rookie year in Cincinnati (9-7 record) and Cam Newton's rookie year in Carolina (6-10 record) is Dalton had a better team around him.
"So much is dependent on your team when you have a rookie quarterback," Arians said. "You need defense and special teams. All the pressure can't be on the offense to score."
Luck is just a rookie, about to get his first real taste of the NFL.
But he is one rookie you'd rather play with than against.