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How good is Seager defensively at 3B?
The big difference between Walker and Polanco is that one was lead glove and the other a GG-caliber defender at 2B and 3B.
Polanco was an Ichiro-level player when he'd hit for average in his good years. He was also consistently a 3-4 WAR player in the other years. The guy has been an impact player and very overlooked.
Todd Walker was generally a league-average player.
If Seager can be Polanco, he could end up having a better career than Justin Smoak. He'd be extremely underrated as a prospect.