First base has long been seen as a power position. Somewhat recent players who played in the American League such as Mark McGwire, Jason Giambi, Mark Teixeira, Carlos Delgado, Paul Konerko, and Jim Thome were power sources, each and every season, for quite some time.
That is not necessarily the case, anymore, as there doesn't seem to be as many offensive stalwarts at the position in the Junior Circuit. At the moment, there aren't as many fearsome first basemen as there were in the past.
With that being said, many will still be important contributors to their team. Here are the rankings for the projected starting American League first basemen according to Roster Resource's depth charts. As a subjective list, it is not easy to rank the players as many can almost be considered interchangeable as to where they are ranked.
Matt Olson, Athletics
Olson (turns 25 on March 29) hit 24 home runs in just 59 games, for the Athletics in 2017. He finished fourth in American League Rookie of the Year voting. He didn't quite sustain that level of power last season but still clocked 29 homers and 33 doubles. Excellent glove work at first base earned him his first Gold Glove in 2018.
Edwin Encarnacion, Mariners
As Encarnacion ages he isn't quite the fearsome hitter he was a few years back. That doesn't mean he can't do damage anymore though. Last year with the Indians, he hit 32 home runs which is the seventh-straight year that he has at least reached that number. While he's listed as the starting first baseman currently, he has been utilized as a designated hitter far more often in recent years.