Starling Marte made his presence well known with his stellar rookie 2013 campaign. In 556 plate appearances, Marte hit .280/.343/.441. Marte showed some power and plenty of speed. He had a dozen home runs with a .161 isolated slugging percentage, but also stole 41 bases. Marte, as well as former Milwaukee Brewers center fielder Carlos Gomez were the only players with 40+ steals and a dozen or more home runs in 2013.
The downside to Marte's game was his plate discipline, drawing walks at a poor 4.4% rate with an unspectacular 24.4% streikout rate. But despite his lack of walks and below average streikout rate, Marte was still a well above average hitter. He had a .344 wOBA, and 122 wRC+. It also helps that he was an outstanding defender with +2 DRS and a +12.8 UZR/150. With a +4.3 fWAR, Marte led all National League rookies.
While the Pittsburgh Pirates are unsure of who takes over one of the corner outfield spots, Ji-Hwan Bae is a safe bet to start the year out in left field. The South Korean prospect has mostly played middle infield throughout his minor league career, but has seen the amount of time spent in the outfield grass increase over the last two seasons.
Bae had a fine season at Triple-A, batting .289/.362/.430. Bae is an extremely fast runner and was in the top 90th percentile of sprint speed during his brief MLB stint. It helps that he hits for average and consistently draws walks. Bae had a 10.1% walk rate with a strikeout rate of just 16.7%, which is the third season in a row he's had a 10%+ walk rate.
Although power is Bae's biggest weakness, he did match his career high home run total last season with eight, and had a career best .141 isolated slugging percentage. During his late-season stint in the majors, Bae collected 11 hits, including three doubles, and struck out just six times across 33 plate appearances. He was also three-for-three in stolen base attempts.
Although Bae has a very good feel for hitting and draws his fair share of walks, it's going to be hard to top a 4+ fWAR season with a wRC+ above 120. That doesn't mean I think Bae will be a poor player, but a 4+ fWAR and 120+ is generally considered all-star level. Marte takes the cake here.