Nelson, 26, hit .250 in 63 games with the Rockies last season, which included a brief run as the starting second baseman before the Rockies acquired Mark Ellis (now with the Dodgers) in a trade.
During Spring Training, Nelson, the Rockies' top Draft pick in 2004 out of Redan High School outside of Atlanta, hit .275 with a .464 slugging percentage, two home runs, five doubles, a triple and 12 RBIs. Versatile Jordan Pacheco hit .339 with a home run, seven doubles and nine RBIs in 23 games.
Manager Jim Tracy said both will get plenty of playing time, but he felt Nelson earned the start Friday not only because of his defense, which is above average at third and good enough at second and short, but his offense.
"Offensively, he's been extremely consistent all spring long -- even his outs at times have been very hard outs," Tracy said. "In relation to where he was at a couple of years ago and where it is he's come to, to be starting on Opening Day, I'm sure he feels good about himself. As well he should."
Pacheco, 26, who like Nelson is on an Opening Day roster for the first time, plays third base, first base and catcher, which makes him a valuable and versatile member of the bench on days he doesn't start.
"There were games in Spring Training where I came off the bench and played the last half of the game, so I'm prepared to do whatever," Pacheco said. "Me and 'Nellie' come to the park ready to play, to do whatever we can to help the team.
"I'm ready for any position. At the end of the day, it's baseball. You've got to field the ball. You've got to catch the ball. You've got to throw the ball. Keep it simple and you'll be all right."