MANKATO - Erin Henderson is taking nothing for granted.

Henderson, entering his fourth season, appears to be a near lock to win the Vikings' weak-side linebacker job and start alongside his big brother E.J. Henderson in the Sept. 11 opener at San Diego. That would make them the first brothers to start a game alongside each other at the position in the modern era.

As interesting as that might be, Erin Henderson isn't focused on such factoids and hasn't done any research on how unique his situation might become.

"I've got to make sure I'm starting beside him before I go do any research or look anything else up," he said. "I'm sticking to my guns right now and just trying to work every day to get better at the little things. I don't really feel like I've got my spot locked up; I don't feel like I have anything secured. I'm just working every day to try to get better and to try to show the team that I'm here, I mean business and I'm in it for the long haul."

Signed by the Vikings as an undrafted free agent in 2008 out of Maryland, Henderson is getting his first real opportunity to win a starting spot in the NFL. It comes as a result of Ben Leber's departure as a free agent -- the veteran has agreed to a one-year deal with the Rams -- and after plenty of ups-and-downs with the Vikings.

Henderson, 25, played in only two games in 2009 and was suspended for the final four games of the regular season for violating the NFL's policy on performance enhancing substances. Last season, he was inactive for six of the first 10 games, including the final five of Brad Childress' tenure as coach. But after Leslie Frazier took over, Henderson played in five of the final six games and contributed on special teams. He missed the season finale because of a concussion.

Frazier served as Vikings defensive coordinator for three-plus seasons before being promoted and has seen Henderson mature as a player and person. "He has really grown up," Frazier said. "He came in as an underclassman, he was a young guy when he came in. Myself and the coaches, we've commented a couple of times on how much he's matured over the last couple of years. We're benefitting from that."

Henderson was a restricted free agent after last season but never had a desire to leave Minnesota once Frazier got the head job. Henderson signed his one-year tender worth $1.2 million shortly after the NFL lockout ended.

"A lot of my issues that I had may have been coach Childress, may not have been, I don't really know what was happening on the inside, what wasn't," said Henderson, who became a father four months ago when his son, Lennox, was born. "I just knew once coach Frazier took over I was [active on game day], there weren't any questions about it. ... And I don't want to leave Minnesota. I love it out here. I enjoy the people, I enjoy the fans, I enjoy the atmosphere."

Obviously, the chance to play alongside E.J., the Vikings' middle linebacker, is a special opportunity. E.J. is six years older than Erin, so the two didn't get an opportunity to play on the same teams during their younger days. It was Erin who held E.J.'s hand as E.J. was driven off the field on a cart after he suffered a broken leg in December 2009 at Arizona.

"I'm as proud as a big brother can be," E.J. said. "He definitely came in and proved himself from being an undrafted rookie to building himself up to being a starter, hopefully. So I definitely commend him for all his hard work. He lives by the same Henderson creed: You want to be the best, you've got to work harder than the rest."

Although Ross Homan is behind Erin Henderson on the depth chart, coaches have said Henderson is battling Jasper Brinkley and Kenny Onatolu for the starting spot. Brinkley, however, is more suited to remain at middle linebacker and Onatolu has been sidelined since last week by a stress fracture in his left foot.

Frazier has been pleased with the younger Henderson's performance in practices, saying he has shown good range, attention to detail and playmaking skills. The Vikings' preseason opener Saturday at Tennessee will provide Henderson his latest opportunity to make an impression.

He plans to make it a good one.

"I'm excited for the opportunity, and I just can't wait to get out there and show them that they weren't wrong and show them that they were right in believing in me and believing that I could be the guy that they need me to be out there," Henderson said. "It's a great opportunity for me and I guarantee you I won't let it slip away."