1. Josh Donaldson (29) - Donaldson vs. Machado is the question for me at 3rd, and with Donaldson moving to a great ballpark and lineup in Toronto I feel like the question has been answered for me. He set a career high last year with 29 homers and even stole a sneaky 8 bases. I'd say you can count on 30 homers in Toronto for the next 3-5 years and he also has upside beyond that.
2. Manny Machado (22) - Machado had a very odd second year in the big leagues. First he started the year with an injury and missed major time, then had a couple of very unusual on field incidents, including one with the afore mentioned Donaldson. In the end he hit 12 homers in 82 games and flashed a little bit of the upside he has at 22. He's not a batting average monster, and he only had a 5.6% walk rate last year, so he's far from a lock to be as good as Donaldson or Adrian Beltre but I'm going to be betting on him.
3. Kris Bryant (23) - Not sure what all to say about Bryant as he is yet to have his first big league AB, but I'm ranking him this high because of the hype around him. If you're in a startup draft there may be no third baseman with more trade value since every team that looks to rebuild will want him or a player like him.
4. Carlos Santana (29) - It feels weird to rank the longtime catcher here, but with only 11 games behind the plate in 2014 it looks like his days of being eligible there are numbered. His value takes a hit at 3rd, but not a gigantic one. He still is one of the best OBP players in the league and last year his career low .231 average was fueled by a .249 BABIP. He's got a career .274 BABIP so he should rebound at BA, and if people are looking to sell due to the position switch I might be looking to buy.
5. Kyle Seager (27) - Did you realize how good Kyle Seager has been the past 3 years? Well he's hit 20+ homers with a .260ish batting average every year, so pretty damn good. Not a "sexy" player but he's solid and in todays fantasy game 25 homers are pretty hard to find, especially from a guy who doesn't kill your batting average.
6. Evan Longoria (29) - Longoria is one the hardest people for me to rank at 3rd. He's got 30 home run power and has hit close to .300 at points in his career, but last year he hit only .253 with 22 homers. Perhaps even more concerning is that his walk rate dipped to 8.1% which is the lowest of his career. Lots of red flags with here, 2015 could be a year when he rises back to the top of the third base ranks or falls off a cliff.
7. Todd Frazier (29) - Who is the Todd Frazier? Is he the monster who nearly went 30/20 last year, or is the guy who hit .234 with 19 homers and 6 steals the year before? The answer to questions like these is almost always somewhere in between, but I can't help but think of Chase Headley when I look at Frazier's 2014. I think the safe play is to bet against Frazier in 2015.
8. Pablo Sandoval (28) - Sandoval makes a huge leap up my ranks with the move to Boston. It's impossible to really know how much moving to Boston will help his power numbers but I'm going to bet he has a realistic shot at 25 homers the next few years which makes him a top ten option.
9. Nolan Arenado (24) - A couple years ago Arenado was one of the hottest prospects in the game, he was hitting .298 with 20 homers in the minor leagues and he just had to have 35 homers in him once he got to the majors.... Except he didn't. He also only hit 12 home runs in AA for the Rockies and their minor league parks are just as power friendly as Coors Field so I think we can safely say he won't be hitting that many bombs any time soon. Even still he's a solid young option that could get you 25 in his prime so he makes the top ten just barely.
10. Adrian Beltre (36) - Beltre has been the best third baseman in fantasy for a while now and had produced 3 monster fantasy seasons in his first 3 years in Texas, but last year he started to slip even so slightly with only 19 homers his worst total since 2009. With age and injury concerns he can't be a top 5 dynasty option at the position anymore.
11. Matt Carpenter (29) - Carpenter was all the rage back in 2014 after his monster 126 run season, then he dipped down to 99 and hit only 8 home runs. He's still a good player, but his upside is limited.
12. David Wright
13. Nick Castellanos
14. Miguel Sano
15. Ryan Zimmerman
16. Chase Headley
17. Joey Gallo
18. Pedro Alvarez
19. Lonnie Chisenhall
20. Mike Moustakas