Herrera has battled his own issues, with his average dropping from .303 on May 7 to .245 going into Sunday, but he had a hit in each of his last three starts. Tracy allowed that if Herrera turns hot and Nelson, who is capable of playing third base and shortstop in a pinch, continues to struggle, the two could interchange roles.
"Today is one of those days where it's somewhat necessary to change them out, to give Chris a chance to catch his breath a little bit," Tracy said. "He's been fighting it the last four or five days, and you're mindful of that. You're putting a guy in that is going to give you a competitive at-bat, maybe not with the same type of power that the other guy provides. But you know the ball's going to be caught and you know that the situations offensively that show up and involve him, you'll know he'll be ready for them. We're giving up very little, and that's a nice thing to know when you've got to make a switch-out like this."
Tracy said with the Rockies having begun a stretch of 17 straight days of games between now and the All-Star break -- thanks to Monday's makeup game against the Cubs at Wrigley Field -- he will be looking for a time to rest his key offensive players, shortstop Troy Tulowitzki and center fielder Carlos Gonzalez.