In 130 game and 486 plate appearances, rookie Addison Russell has hit .238/.301/.389. His wOBA is .302 and his wRC+ sits at 88. As a 21 year old who is now firmly planted at shortstop, those are some pretty good numbers. As a Major League hitter, they're below average, but the age and position matter a lot. He's hit 13 home runs already and has a .152 ISO. I've not only been surprised that his defense has been as good as advertised, but that he also can hit for power. It's not power projected down the road, but immediate power.
It wasn't long ago that the Cubs had another bright young shortstop and I thought I'd compare the two. I'll compare Russell's rookie season to Starlin Castro's, but Castro was a year younger and played shortstop the entire year. It wasn't really Russell's fault he didn't play the position all year long, but that's another story altogether. I'll also compare what Castro did through his age 21 season (2010 and 2011) since Russell is 21.
Neither were particularly good base-stealers in their rookie season and neither ever will be. There are two things that really stand out when looking at that table: Russell has hit 10 more home runs and he's struckout twice as frequently.
For BB%, I almost always use this formula: (BB-IBB+HBP)/(PA-IBB)
Castro had the better overall season offensively, but patience and power are probably the two most important things offensively. Russell has been better in both those areas. By quite a lot. To top it off, Russell has been the far better defender too.
Castro had a really good age 21 season in 2011. Combined between 2010 and 2011 Castro hit ..304/.343/.422 with an OPS+ of 106. He hit 13 home runs in over 1200 plate appearances, which is equal to the amount Russell has hit in under 500 plate appearances.
Though Russell's numbers don't stand out like Castro's did, Russell has shown that at the very least, he's as good as Castro offensively, but probably better. There's a lot to like about Russell and there was a lot to like about Castro too. Castro's lack of patience was always a concern.
Also worth comparing is the batted ball rates. Castro was an extreme groundball hitter and still is (even more so now). Over 50% of his balls in play were groundballs. Only 40.7% for Russell. Russell's GB/FB ratio is 1.01 while Castro's was 1.76. Castro's is 1.96 this year. Only 29.2% of Castro's balls in play were fly balls compared to 40.4% for Russell.
Castro swung at 33.7% of the pitches of the zone according to Fangraphs Pittch F/X Plate Discipline. Russell has swung at 29.8%. Russell has swung at more pitches overall and made less contact. Russell will have to reduce his strikeouts in the future to reach his potential, but he's better positioned to reach that potential than Castro was in my opinion.