Your pitching isn't horrible and anyways, I like going bargain bin hunting with my pitchers and making gains in hitting categories as much as I can early in drafts. Cobb and Estrada could be there for you in a big way. Detwiler, Ogando or if somebody bails on Clay Buchholz early could help you more than having Grilli.
On second thought, I really like Cuddyer this year. I took him really late in a couple drafts figuring a bounce back was in order and that he probably has too much pop to not put up at least one really nice season in Coors. I didn't bother to look into it too much and having done that I'm not saying people need to hunt him down, but he's a sick bench option if you're going to go high risk/high reward at 1B with a guy like Napoli, or even a Morneau or if you might have an opening at UTIL at some point in the season. He'll play his way off your bench.
As for who your best third basemen is, when you're dealing with guys with limited ML experience, it's tough to figure out. Machado is super young. That's great for the O's, not great for fantasy. I also think looking at career minor league numbers can be misleading... but, if you know what you're looking for you can cherry pick your way to an answer with those numbers but without getting to in-depth about it I think it's safe to say Machado is a couple years away from making a big fantasy impact.
IMO, AA is where hitters really get challenged for the first time by pitchers who can control a FB and at least one off-speed offering. 400 PA's of AA experience is enough time to at least get a vague idea of a guys potential. As a 20 year old, when Longoria got to AA he didn't light it up. The following year though, he got 447 PA's in AA to start the year and burned the league to the ground with a .307/.403/.528 line which is great. Machado was two years younger than Longo when he got his introduction to AA, and went .266/.352/.438. Those are great numbers for a 19 year old, but the .438 SLG against AA pitchers as a 19 year old suggests he's probably a year or two away from being able to consistently hit for power in the Bigs. He's a better prospect than Middlebrooks, but Middlebrooks might be more major league ready. In 2011 over 397 PA's he went .302/.345/.502 against AA pitching and kept it going starting the next year at AAA and dropping a 1.000 OPS in 100 PAs before getting called up to the bigs. Middlebrooks is a better hitter right now. He's a lot more likely to have what it takes to be a reliable fantasy 3B right now.