Still others arrive lost and stay that way for a year or 2 or 3 before the light finally goes on and the game slows down for them.
It's still too soon to determine which of those categories Nick Foles will fall into. But judging from his impressive play at training camp and in the Eagles' first preseason game, it probably won't be the last one.
"He's got an opportunity to be a heckuva quarterback at some point," said Mornhinweg, the Eagles' offensive coordinator. "He's smart. He's talented. He picked the offense up at a pretty good rate here.
"He's quite a natural player. A quick decision-maker. Accurate. And his timing has been good up to this point. But he's still got a lot of work to do at this point. His challenge is to continue to progress at a high rate."
So far, so good. Foles, the Eagles' 6-6, 243-pound third-round pick, threw two touchdown passes and averaged 14 yards per attempt in a quarter of work against the Steelers last week.
And as luck would have it, with Mike Kafka expected to miss at least the next two preseason games after fracturing his non-throwing hand in the Pittsburgh game, Foles now is getting an opportunity to work with the second-team offense.
If he continues to play well, it is possible, if not probable, that the rookie could open the season as the team's No. 2 quarterback behind Mike Vick.
"We'll see," Mornhinweg said. "If he continues to develop at a high rate, that will be the key for him.
"His accuracy has been really good. If you see an errant ball on occasion, in most of those cases, it's because he was unfamiliar with the play and he wasn't staying true to his read or his progression, and then all of a sudden, he has to throw the ball away or the pass-rush gets to him and he's errant because he wasn't quite quick enough.
"But I have felt very comfortable with him when he knows exactly what he's doing in a particular play. I think he's executed at a high level.
"His challenge is the whole offense and getting all those reps, because it appears he's quite a natural player."
Foles was the 88th overall pick in the April draft and the seventh quarterback gobbled up, after Andrew Luck (Colts, No. 1), Robert Griffin III (Redskins, No. 2), Ryan Tannehill (Dolphins, No. 8), Brandon Weeden (Browns, No. 22), Brock Osweiler (Broncos, No. 57) and Russell Wilson (Seahawks, No. 75).
Foles broke just about every passing record at the University of Arizona.
Many pro scouts felt he had first-round talent - strong arm, accurate, sturdy body, good decision-maker. But there were some concerns about his mobility, as well as the fact that he played for a team that won just four games last season.
"There were a couple of concerns I had," Mornhinweg said. "But [quarterbacks coach] Doug Pederson went out [to Tucson] and worked him out, and my concerns were negated by Doug working him out."
Despite his size, Foles, a high school basketball player, has displayed ample mobility. In the preseason game against the Steelers, he was flushed from the pocket and managed to complete a 70-yard touchdown pass to wide receiver Damaris Johnson.
The Eagles also had their eye on Wisconsin's Wilson, who happens to be more than 7 inches shorter than Foles, in the third round. It's unclear which one of the two they would have taken if both had been available at 88.
Regardless of what ultimately happens with the backup quarterback job, the next couple of weeks are going to be invaluable for Foles as he takes his rookie education to the next level.
"Of the many plays that have been installed, he hasn't quite gotten the reps at these particular plays," Mornhinweg said. "Or maybe he's gotten just one rep and it was 2 weeks ago against a particular coverage. Well, now he's got to get through that particular play against all of the possible coverages and blitzes. So it's a matter of reps, reps, reps and a basic fundamentals in the details in how he goes about performing."
Said Foles: "Just getting more reps is invaluable. I'm getting to run more plays. I'm getting to run plays that I haven't necessarily repped a lot or repped at all. I know I repped some today that I hadn't repped at all. I've just seen Vick and Kafka rep them. So it's good for me to experience those plays and sort of put them in rhythm and see what it feels like."
While Kafka's injury is helpful to Foles as far as getting more quality practice reps, it also appears to put veteran Trent Edwards back in the backup quarterback picture.
Mornhinweg insisted Monday that Kafka's injury won't have any impact on his chances of winning the backup job. "Because we know exactly what [Kafka's] strengths are and how he can help this football team, I don't see this as a knockout for him," he said.
But Kafka hasn't had a particularly good camp and didn't play all that well against the Steelers. If the Eagles ultimately decide he just isn't good enough to be a heartbeat away from the starting quarterback job - in a year they feel they're good enough to make a Super Bowl run - and they aren't completely comfortable with the idea of giving the No. 2 job to a rookie, Edwards is a fallback option.
He is the only quarterback in camp besides Vick who has started an NFL game. Thirty-three of them, to be exact. Edwards, who has been getting the fewest reps in camp, doesn't have the physical tools Foles does.
But he knows how to run an NFL offense.
"Trent's a gamer," Mornhinweg said. "He's got great experience. He wouldn't have been in the league this long, wouldn't have started and done quite well in this league without what you saw that he had the other night. He did exactly what I wanted him to do, with the exception of a couple of small details."
Edwards played the fourth quarter against the Steelers. Threw one touchdown pass and engineered a late 11-play, 46-yard drive that set up Alex Henery's game-winning, 51-yard field goal.
"You saw he's a natural player," Mornhinweg said. "He's got great common sense and he did just a beautiful job down the stretch there. He doesn't get many reps in practice. He understands what his situation is, and then he knows the expectations of him going into a game is to play at a high level. It's just that simple."
Deciding on who will be the Eagles' season-opening backup quarterback, though, isn't.
Contact Paul Domowitch at email@example.com