(Eds: Updates. With AP Photos.) By ERIC OLSON AP Sports Writer Justin Jackson had just one question for Nebraska's coaches when they asked him last winter if he would be willing to change positions for a third time.
''I asked them if I had an opportunity to play,'' he said.
Of course, they told him - if he earned it.
That's all he needed to hear. Jackson agreed to move from defensive tackle to center and competed against two more experienced players in spring practice and fall camp. He appears to have won out.
Coach Bo Pelini put Jackson on scholarship two weeks ago and said the fifth-year senior is the front-runner for the starter's job in Saturday's opener against Southern Mississippi.
''It would mean the world to me,'' Jackson said.
Jackson is the quintessential Nebraska walk-on. He grew up 20 minutes south of Memorial Stadium in Roca, Neb. He turned down scholarship offers from FCS and Division II programs to follow his dream of playing for his beloved Big Red. He was Pelini's first walk-on, in 2008, after he earned all-state honors in Nebraska's second-largest high school division.
''I don't consider myself a second-rate athlete because I walked on,'' Jackson said. ''I just took a different road than other people. I never sold myself short and never expected anything less than perfection from myself. Did I reach it? Definitely not. I have yet to put together a perfect practice out here. But I strive for it and work for it.''
Jackson's determination has not gone unnoticed by teammates. Several fellow walk-ons told him that his perseverance inspired them to work harder.
Jackson's career floated in limbo until this year.
He sat out as a redshirt in 2008 and appeared in mop-up duty on the defensive line in a total of three games in 2009 and `10.
He was moved to guard for the start of last season but didn't play in the first eight games. He switched back to the injury-thinned defensive line in late October and got into games against Northwestern and Iowa.
After the season, with starting center Mike Caputo having graduated, Jackson was called on to compete against Cole Pensick and Mark Pelini.
''I wouldn't be where I'm at without Mark and Cole,'' Jackson said. ''It's unbelievable how big a help they've been. Being the competitor I am, if someone was gunning for my spot, sometimes I don't know how much I would help him out. I've learned a lot in my leadership skills from them. I promise you I wouldn't be where I am without them.''
Tight end Ben Cotton said Jackson has more than just blended in with the offense. He's been a take-charge guy.
''There are obviously days when some guys might be feeling down or sore, but guys like Jackson are there to get everyone's motor running,'' Cotton said. ''He does a very good job of that because he plays at a very high level, whether it's an offseason shake-out run in the summer or it's during game time. He is at the same level no matter what he does.''
Jackson said he's still flabbergasted at how his career turned so quickly, from being someone who rarely made it onto the field to being the probable starter for the opener.
''I knew that walking on to this university, no one owes you anything. You never forget that,'' Jackson said. ''You have to come out here and prove it. I always knew that I could play for this university and have always had a chip on my shoulder to come out here and prove it every day.''