Editor's note: Now that free agency has started, Keith Law picks out possible best values, worst values and trade targets across every position group. He started with the catcher position Sunday, followed that with corner infielders and middle infielders, and now continues the annual series with a look at the outfielders who have hit free agency, as well as some potential trade targets.

For the top 50 free agents across every position, click here.

The first three position areas I covered in this offseason's buyers' guides were all very thin, at least on the free-agent side of things. The outfield market, however, is loaded with free agents on the corners, while there are a couple of center field options who are or might become available in trade.

Top free agents

Jason Heyward, RF/CF: Heyward is the top free agent in my rankings for two reasons: He has been extremely valuable so far in his career thanks to superb defense and solid to great on-base skills; and, at 26 years old, he's just entering the typical peak period for position players. That should drive tremendous interest in his services, especially coming off a season in which he posted the best batting average and lowest strikeout rate of his career. But it also gives potential employers reason, or perhaps a mix of reason and unreason, to hope for a better return on their investment than they might get from a typical top position-player free agent: He should hold his value longer, and there's even a chance he'll continue to get better. The Cardinals worked on his mechanics to improve his contact rate, but there's still untapped power in there and a history of better walk rates. There are rarely bargains at the top end of the free-agent market, but Heyward at least offers the opportunity for good value.

Justin Upton, RF/LF: Upton is a bit of a poor man's Heyward, a fairly young (28 entering 2016) position player who has tremendous tools and has shown star-caliber performance for brief periods but who hasn't put it together for a whole season since 2011. He has 30-homer power, he has drawn walks in just over 10 percent of his career plate appearances, he has great bat speed, he has played above-average defense in some years of his career ... and if you get one of those seasons when he does it all at once, you have an instant MVP candidate. He was a 6-WAR player once, and while that was four years ago, the physical tools are there for him to do it again. You just don't want to pay him on the assumption that he'll do it every year.