This is getting SO frustrating. They need to stop giving Morgan the green light to steal if he's going to get thrown out half the time!
They need to talk to him about stealing off Olivo. Show Olivo some respect.
That said, Riggleman addressed this in an interview after the last Rockies series.
Q: [Nyjer Morgan]'s been caught stealing in 3 of 7 stolen base attempts so far, is there a point at which you're going to rein him in?http://www.federalbaseball.com/2010/4/24/1440125/ask-washington-nationals-skipper
Jim Riggleman: "No. The Rockies are very tough to run on. They do a great job of holding the runner at first base, your timing and all that, get you out of your rhythm, they do a great job of it as some other clubs do, but you combine that with the way [Miguel] Olivo's throwing and it's just tough. Really what you've got to do is just hope that he's running when the pitcher gives you a pitch to hit so that the hitter is swinging, it just so happens he's run when Jimenez yesterday didn't throw a strike, so the catcher got a great ball to work with, kind of up, and he's got a great arm, so you've got a quick time to the plate, you've got a catcher with a great arm, the pitch is 97mph some times, so it's kind of a guessing game. The runner is maybe hoping breaking ball, he's maybe hoping the fastball is the ball there to be hit so it becomes like a hit and run type of play, and it just hasn't fallen into place. If I put the reins on him, then it's just, his value to us goes way down if I hold him up too much."