SAN FRANCISCO -- Acquiring a proven outfielder or two is more than just a possibility or even a priority for the Giants during this offseason. It's virtually a necessity.
Last season's Opening Day outfield of Andrew McCutchen, Austin Jackson and Hunter Pence evaporated through trades and free agency. Gorkys Hernandez wasn't tendered a contract dspite hitting 15 home runs and appearing in 142 games in 2018. Gregor Blanco was not retained, despite his versatility and team-first attitude.
That left the Giants with Steven Duggar, Chris Shaw, Austin Slater and Mac Williamson. Duggar is next year's projected starting center fielder but first must overcome a shoulder injury. Williamson and Shaw are prone to injuries and strikeouts, respectively. Slater recorded a .307 slugging percentage in 225 plate appearances last season.
But don't single out any Giants outfielder for his shortcomings. Any lack of production was a collective effort. Among National Leaguers, Giants outfielders ranked 14th in runs, last in home runs and 14th in OPS.
So even from the fairest perspective, San Francisco's outfield remains short on depth and quality. Fortunately for the Giants, they don't have to sign Bryce Harper, this offseason's premier free agent, to achieve an upgrade. Michael Brantley, a three-time All-Star who recorded a .309/.364/.468 slash line last season with Cleveland, is still available in free agency.
Moreover, a sizable number of outfielders appear to be candidates for potential trades. A list of several possibilities follows:
Domingo Santana, Milwaukee: He's frequently mentioned in trade rumors after slumping to five home runs in 85 games this year following 30 homers in 151 games in 2017. The Giants could entertain obtaining him for Joe Panik, since Milwaukee needs a second baseman. Santana would also fit nicely in the Brewers' package if they were to try to trade for Madison Bumgarner.

Nicholas Castellanos, Detroit: He has hit 67 home runs in the last three years, far more than any Giant. However, he's eligible for free agency after this season.
Jason Heyward, Cubs: San Francisco was believed to have interest in Heyward during the 2015-16 offseason, when he signed an eight-year, $184 million deal with Chicago. The Giants ultimately signed Denard Span.
Derek Fisher, Houston: This would be a wager on Fisher's mostly untapped potential, which he is said to possess in abundance. He has hit .196 in 252 plate appearances spanning the last two seasons, but he's only 25.

Hunter Renfroe, Padres: Though the Padres have a glut of outfielders, they'd probably be reluctant to trade within the division. If San Diego were inclined to make such a deal, the Giants might ask for Renfroe, who has six of his 56 career homers against San Francisco.
Odubel Herrera, Phillies: He or fellow outfielder Nick Williams could come west in a Bumgarner deal. Herrera, a 2016 All-Star, has hit 51 homers in the last three seasons, including 22 in 2018. Williams has 29 homers and a .269 average in two big league seasons.