Zarek Valentin faced the first serious challenge of his budding soccer career at the age of 15 when he was cut from the U.S. Soccer Residency Program in Bradenton, Florida.

In that difficult moment, one of Valentin's coaches pulled him aside. He told the teenager to take a notecard and write down three things that made him a good player and what he needed to do to excel in those areas. Valentin read that notecard before every training to put himself in the right space psychologically. That's how he first began to embrace the mental side of the game.

In 2013, he rewrote his notecard with three key concepts: Be a great passer, great defender, great communicator. He still reads the handwritten, laminated card twice before every match.

"I remind myself if I do those things and control what I can control and try to help the guys around me, then that's doing my job," Valentin said.

Reading that notecard is part of a deliberate pregame routine that Valentin has cultivated over the years to ensure that he has the right mindset before going out on the field. But he said that a slight tweak in that routine has enabled him to become even more successful with the Portland Timbers this season.

After listening to an interview with NBA star Lebron James this offseason, Valentin decided that he was gearing up for games too early. Now, he tries to stay loose and be himself up until 45 minutes before any match. He'll listen to calming singers like Stevie Wonder, Ray Charles and Aretha Franklin and joke with teammates in the locker room. Moments before going out for warm-ups, he'll finally read his notecard and start to intensely focus in on the game.

"I've been a lot more calculated about my decisions this year, about my preparation before games mentally more than anything," Valentin said. "I think it's helped me be sharper when I get into the game and a little bit more intense. Mentality-wise that's been the biggest thing that I've consciously tried to do differently."

Having the right mindset has been particularly important to Valentin this season as he has claimed a starting role in a new position.

While Valentin mostly played as a right back or left center back in previous years, the right-footed defender found himself thrown into the left back role early this year after a preseason injury to Vytas left an opening at the position. The Timbers traded Vytas to D.C. United Wednesday.

Valentin has started in 19 of the club's 20 games this year and has developed into a consistent defensive presence and vocal leader on the left side of the pitch. While he doesn't get forward in the attack as often as a natural left-footed defender might, Valentin has taken great pride in being able to shut down his man defensively.

"He's earned every minute that he's played," Timbers coach Giovanni Savarese said. "He understands what we ask him to do and executes it. Every time we throw something new at him, he does it."

Valentin has grown more comfortable in his new role as the season has progressed and Savarese has taken notice. The Timbers coach has pushed his new left back to expand his role in recent weeks, asking Valentin to get forward in the attack more often or even play as a wingback. The 27-year-old has embraced every new challenge, while remaining focused on the key ideals that have allowed him to be successful on the field.

In the coming weeks, Valentin's role could change. The Timbers announced Wednesday that they had reacquired left back Jorge Villafana from Liga MX side Santos Laguna. Villafana was a critical part of Portland's MLS Cup title run in 2015. With Villafana returning to the club, Valentin will have to compete to maintain a starting spot at either the left back or right back position.

But the role that Valentin has played in Portland's success this season cannot be overlooked.

Portland (10-3-7, 37 points) is riding a 15-game unbeaten streak and currently sits in second place in the Western Conference standings. With Valentin confidently embracing his job at the left back position, the Timbers have posted six shutouts this year and have the fewest losses in all of MLS.

"I just go out and try to perform my role to the best of my abilities," Valentin said. "I hate the saying, 'Do your job' because it's from the Patriots, but I use it a lot. Do your job and then if everyone does their job collectively that's how the team will succeed. That's what I've tried to focus on, just doing my job."

-- Jamie Goldberg | jgoldberg@oregonian.com

503-853-3761 | @jamiebgoldberg