Blake's had a good, long career, and there's a chance this release was purely that he might catch on with another team before the Spring runs out.
The door is wide open for any number of young players to take a starting position and hold it tightly. Nolan Arenado had about as bad of a spring as Pacheco is having a good one, so he's pretty much a lock for AA Tulsa. Herrera is definitely making waves with a >.900 OPS this Spring.
Outside of the expected candidates, Andrew Brown did play a little 3B in 2010 down in AA Springfield and Brendan Harris' .360/.407/.440 line and actual ability to play the position could make him a contender as well.
Don't forget that Michael Cuddyer has played 3B with Minnesota, and we have guys who can take the RF spot having big Springs as well.
If Arenado continues his prodigious rise through the minor leagues, this could just be a temporary inconvenience.
* * * UPDATE * * *
I'm hearing that Blake's body is just giving up on him. He's been in pain most of Spring Training. This could be the end for Blake, which makes me sad. That beard alone is worth at least 1 WAR.