Kelsey Martinez breaks ground as Raiders’ first female assistant coach

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Kelsey Martinez crawled at five months old and walked at nine months, says her mother, Khris Fuentes. She rode her first bike without training wheels. She hated being inside and spent much of her childhood in Pueblo, Colo., outdoors and playing sports.

“She was in the trees, she was playing baseball, you name it,” Fuentes said. “Everything that the boys could do, she could do.”

And still, when Martinez told her mother she intended to pursue a coaching job in the NFL, Fuentes figured there would be challenges.

“I told her, ‘That’s great, and I want you to have goals like that, and I hope you can achieve that,’” Fuentes said. “ ‘Just know that’s a male-dominant type of career — or not even really career, just atmosphere.’”

That conversation, Fuentes said, happened a little over a year ago. Martinez is now in her first season as a strength and conditioning assistant for the Raiders. She’s the first female assistant coach in the team’s history and the only female strength coach in the NFL. Sunday, her family and friends will make the trip to Denver to watch her at work as the Raiders play the Broncos.

At 26, Martinez is once again the embodiment of forward progress.

Oakland Raiders strength and conditioning assistant coach Kelsey Martinez watches players stretch during a morning practice at the team's headquarters in Alameda, Calif. on Friday, Sept. 14, 2018. Oakland Raiders strength and conditioning assistant coach Kelsey Martinez watches players stretch during a morning practice at the team's headquarters in Alameda, Calif. on Friday, Sept. 14, 2018. Photo: Paul Chinn / The Chronicle Buy photo Photo: Paul Chinn / The Chronicle Image 1 of / 7 Caption Close Kelsey Martinez breaks ground as Raiders’ first female assistant coach 1 / 7 Back to Gallery

In the NFL, it seems, the times are catching up.

Five years ago, there were no women in full-time roles on NFL coaching staffs. Currently, there are three — Martinez, Katie Sowers with the 49ers and Phoebe Schecter with the Bills.

Lee Brandon was the NFL’s first female assistant strength coach with the New York Jets in 1990. Jen Welter became the NFL’s first female position coach in 2015 when she was hired by Arizona to coach linebackers in training camp and preseason. Kathryn Smith became the first woman in a full-time NFL assistant coach role in 2016, as a special teams quality control coach for Buffalo.

Sowers was hired by the 49ers as an offensive assistant in 2017, becoming the league’s second female full-time assistant coach and the first openly gay NFL coach. Buffalo appointed Schecter to a season-long coaching internship last month, assisting the Bills’ quality control coaches.

It’s progress, said Sam Rapoport, the NFL’s director of football development, whose efforts to broaden the pipeline into NFL football operations include creating the Women’s Careers in Football Forum in 2017. She said in a phone interview the forum is “seeing some good results” and the ultimate goal “is to normalize women on the sidelines in football.”

“Kelsey is certainly a first, and it was monumental when she was hired,” Rapoport said. “We certainly want to celebrate firsts. But then we want to move on and let these folks do their jobs and impress the people that they need to, like every other candidate and intern and temporary employee.”

In August, during training camp, Martinez said attention accompanying her groundbreaking role is “something that has come with the territory a little bit.” But she has remained focused on the job itself.

“How I got here, I’m not surprised in a sense, just because I got to see, first of all, the athletes work, and then their coaches work with them,” Martinez said. “I was like, this is something, if you want to do it, you can do it. The only person that can stop you is you.”

After high school, Martinez attended Bethany College in Kansas for a year, playing softball, then transferred to Colorado State, entering its health and exercise science program. She landed an internship, and later a job, at Tom Shaw Performance in Orlando, Fla., working with athletes at levels including the NFL and, Shaw said, managing the regimens of more than 40 MLB players.

Shaw was hired this spring by head coach Jon Gruden as the Raiders’ strength and conditioning coordinator, and said that before filling out the rest of the staff, Gruden sent trusted aide Mark Arteaga to Orlando to watch Martinez work with athletes. The report back was positive.

“The biggest thing is she has the ability to help guys get better,” Shaw said in August. “Believe me, if she didn’t know what she was talking about when she talked to them, and didn’t know the program, they would find somebody else to go to. … I think in the NFL, that’s what you have to do — you have to prove yourself in order to be accepted. And she’s proven herself.”

Martinez usually leads part of team warm-ups in practice and monitors practices to give player- or position-specific feedback. Off the field, she works with players in the weight room and speed and agility drills. She also learns about their backgrounds to help broaden the coaching staff’s knowledge of individual players.

Tight end Derek Carrier said he thought little of it when he learned the Raiders had hired a female strength coach.

“I’ve been in positions before where we’ve had female athletic trainers,” Carrier said. “To the outside world, I feel like it’s a big thing. But at the end of the day, if people can do their job, it doesn’t really matter who they are or what their background is. She’s an awesome strength coach, and that’s perfectly how it is.”

Going into her first NFL job, Martinez said, she felt “confident in what I was doing.”

“In the beginning, you have to build everyone’s trust as players,” she said. “Now we’re just getting them in and out, making sure they’re getting stronger, faster, more explosive. And when they buy in, it’s easy to do that.”

Martinez is now immersed in the grind of her first season. Still, having spent the past few years living in Florida and California, she said she’s looking forward to Sunday’s game in Denver, where she expects more than 20 family members and friends in the stands.

“It’s like a homecoming game for me,” Martinez said.

Fuentes said she attended plenty of Broncos games in the past. Sunday’s will be different.

“It’s going to be so exciting,” said Fuentes, Martinez’s mother. “A lot of people ask me if I’m now a Raiders fan or if I’m a Broncos fan. And I usually tell them, ‘I am a fan of my daughter.’”

Matt Kawahara is a San Francisco Chronicle staff writer. Email: mkawahara@sfchronicle.com Twitter: @matthewkawahara