SCOTTSDALE, Ariz. - Arizona Fall League rosters are filled with major-league prospects, and the managers of the six teams must somehow afford playing time to each.

The nature of the league ensures that talented young players accustomed to everyday roles are relegated to watching from the dugout much more than usual. Catcher Andrew Knapp, the Phillies' breakout minor-leaguer of 2015, was no exception.

But in Knapp's case, that's not necessarily a detriment. The six-week extension to his already marathon season provided more time outside of games to work on his defense, the aspect of his game that likely will dictate when he reaches the major leagues.

Midway through the fall league schedule, Phillies minor-league catching coordinator Ernie Whitt made a weeklong visit to the desert to work with Knapp. Receiving and footwork were focuses. "Nothing too drastic," Knapp said, but valuable instruction nonetheless.

"During the season, you can't really get in and do stuff like that because you're catching every day," Knapp, 24, said before playing in the league's Fall Stars Game on Nov. 7. "It's good to get in the cage and work with Ernie on some stuff, just some fine-tuning, and when you catch every other day it keeps your legs fresh.

"We're not trying to burn anyone out here. It's been a long year. . . . I think it's been the right amount of catching."

Catching, mainly whether he can do it at the level of an everyday major-leaguer, has long been the biggest question regarding Knapp, the Phillies' fourth-best prospect according to Baseball America. His ability to hit from both sides of the plate is his best asset, but will his defense catch up enough to his offense to the point where he will stick behind the plate?

Knapp still envisions himself as a major-league catcher. "Definitely," he said. He gravitated to the position at a young age, a kid wanting to emulate his dad. His father, Mike, spent 11 years as a journeyman catcher in the minor leagues, mostly in triple A, but never got a big-league call-up. For much of the first five years of Knapp's life, he and his mother followed his father around the minor leagues. He had been to 38 states by the time his father retired from playing in 1996.

"I just like being in every play," Knapp said of his affinity for the catching position. "I think I'm a smart player. I like being in control of the play calling and pitch calling. It's where I want to be. It's where I'm most comfortable."

The Phillies have a decision to make in the next couple of years regarding their catching position. Two of their top five prospects, Knapp and Jorge Alfaro, are catchers whose offense is ahead of their defense. Both will enter the season as catchers, Knapp likely at triple A and Alfaro likely at double A, and continue their development at the position.

Perhaps there is a creative solution to the position surplus, new general manager Matt Klentak said earlier this month. "We don't necessarily have to have the classic 'starting player, backup player,' " Klentak said. The team's front office will cross that bridge when it gets there.

Alfaro, the Phillies' best power-hitting prospect, is so athletic for his position and has such a cannon of an arm that there is a school of thought that he could end up in right field. Knapp dabbled in playing first base and right field in college at California. He played first base in the fall league when one of the two other Glendale Desert Dogs catchers took turns behind the plate.

Knapp caught 94 games in 2015, more than double his previous career high. After he did not catch as much as expected during his three years at Cal, his development was set back in October 2013, four months after the Phillies made him the highest-selected collegiate catcher (53d overall) in the second round of the draft. That was when his elbow blew out on a throw to second base during instructional league play. He needed Tommy John surgery.

"I think his defense will come around. I don't have any question about it," said Knapp's fall league manager, Bill Haselman, a manager in the Los Angeles Dodgers farm system and a former big-league catcher. "He just needs to see the reps. He just needs time behind the plate, and the more the better. He'll be just fine."

The consistency in Knapp's throwing lags behind his receiving and blocking, although his arm is said to be stronger than before the surgery. His transfers on throws to second could use work. But for all the attention on his offense in 2015 - a .360 average and 11 homers in 214 double-A at-bats tends to have that effect - Knapp believes he made strides defensively, too.

And yes, he has thought about reaching the major leagues as early as next season.

"I think you've got to set your goals high," he said. "It's going to be up to me to go out and play the way I need to play. I don't think it's going to get handed to me at all. I need to go out and continue what I did in Reading and win a spot. I think it's definitely a possibility. But it's up to me to put the work in and get ready."

@jakemkaplan