Man if i were Montero i would be worried that Nieves could get more playing time. The thing Montero has going for him is his large contract. Don't get me wrong Miguel is one of my favorite D backs but i hope he starts hitting soon.
The D-Backs don't play their best players, as most teams don't. The loyalty is confusing. I don't know why, but it always comes down to dollars. Go to this link and see where the value truly is in terms of $$$
http://espn.go.com/mlb/team/salaries/_/name/ari/arizona-diamondbacks
It's mostly at the bottom.
Why are Josh Wilson, Cliff Pennington, and Eric Hinske even on the roster? Owings is hitting lights out in AAA and yet he is being bumped by the likes of those clowns. Matt Davidson is another one. Skaggs vs. McCarthy is another one. Nieves vs. Montero is another one.
I know Owings and Davidson play SS and 3B respectively, so you're not going to bump Prado and Didi, but I would play the players that give the team the best chance to win when they get playing time. I'm sure overall Owings and Davidson are better options than Wilson and Pennington. Find a spot for them.