Column: Quarterback K.J. Costello is out to take Santa Margarita to the next level

Harry Welch, the former football coach at Santa Margarita High, uses a horse racing analogy to explain the development of quarterback K.J. Costello.

“When I first saw him as an incoming ninth grader, he was a gangly thoroughbred colt,” Welch said. “There were elbows, big feet, a gangly neck. I could see here was someone who one day could run in the Kentucky Derby.”

Costello always appreciated Welch’s expectations for what he might become as an athlete.

“I feel Coach Welch had a vision of what he wanted me to be,” he said.

Costello enters his final season of high school football as a 6-foot-5, 215-pound senior with a scholarship waiting for him at Stanford, a 4.2 grade-point average and a resume that includes 3,123 yards passing and 23 touchdowns as a junior at Santa Margarita.

Welch, who retired after the 2013 season, likes the path Costello has put himself on.

“As I continue to watch him, he loves what he’s doing and continues to mature and grow and hasn’t come close to plateauing,” he said. “I worked on his feet. I worked on his release. I worked on him understanding defenses. He was like a sponge.”

Welch allowed Costello to start on varsity as a sophomore, and it was a challenging time. Costello had 13 touchdown passes and 14 interceptions while taking over for standout Johnny Stanton during a 4-6 season.

“I didn’t know any other way to do it other than to put him out in the fire,” Welch said. “He had the right stuff but it was going to take time. I could see it. It was there. It was always there. It was going to come to fruition but he had to go through growing pains. I was very tough on him. I would never back off.

“I would expect him to stand up as someone who deserved be in Johnny Stanton’s shoes even though I knew he wasn’t quite ready. He threw some of the best passes I’ve ever seen with people in his face, about to get smacked, and completing balls with authority and getting back up.”

Last season, under first-year Coach Rick Curtis and offensive coordinator Jeff Grady, Costello ran a spread attack and became more proficient at reading defenses and finding open receivers.

“He took studying defenses to a whole another level,” Costello said of Grady’s contributions. “Going up to the line of scrimmage, I actually knew most of the time what I was looking for. I feel my relationship with him has really helped my game move to the next level.”

Improvement in Costello’s mobility and release are two areas that should greatly benefit the Eagles this season. He’s going to be more willing to run if the opportunity presents itself, and with his size he might surprise a linebacker or two with his quickness.

“He has better feet than people acknowledge,” Welch said.

Costello’s father, Kevin, was a quarterback at Crescenta Valley, and he passed along ideas about “how to be a leader the right way, not faking it and meaning what you say,” Costello said.

“This year is 100% for my team,” he said. “I’m a team-oriented guy. We’ve yet to win a playoff game in my career as a quarterback. That’s a huge goal of mine. I feel the only way we’re going to do that is with everybody, and it’s my responsibility to make sure they know I’m all in 100%.”

Welch is going to be traveling around the world enjoying his retirement, but he’s going to keep track of Costello’s progress.

“I believe my expectations for him were so so high because I believed in him,” he said. “With his great work ethic and Jeff Grady’s mentoring, he’s come along. He has a chance to be someone we’ll talk about over the next few years.”

eric.sondheimer@latimes.com

Twitter: LATSondheimer