First base: Carlos Santana, Cleveland Indians
Santana's role with the Indians has been in flux since 2013, as he has converted from catching to third base to first base/designated hitter duties. He had 92 starts as a DH last year with just 62 at first, but over the past three seasons he's started 287 games at the position. In that time, he's been worth 7.1 WAR, with a pair of big seasons in 2014 (3.0 WAR, 122 OPS+) and '16 (3.0 WAR, 121 OPS+) bookending a subpar '15 (1.1 WAR, 101 OPS+). Overall in those years he's averaged a 115 OPS+, 27 homers, 107 walks and even seven steals per season.