Keller hasn't let a lack of size (5-feet-10, 170 pounds), keep him from making a big impact in the NHL. The native of Chesterfield, Missouri, is among the new generation of small, nimble forwards such as Patrick Kane of the Chicago Blackhawks and Johnny Gaudreau of the Calgary Flames who have the skill to beat bigger opponents without taking a pounding.
After breaking Phil Kessel's all-time record for points by a player in the U.S. National Team Development Program from 2014-16 (189), Keller was selected by the Arizona Coyotes in the first round (No. 7) of the 2016 NHL Draft. He played one season at Boston University, finishing with 45 points (21 goals, 24 assists), and helped the United States win the gold medal at the 2017 IIHF World Junior Championship before signing with the Coyotes on March 26, 2017. Three days later, Keller had an assist in his second NHL game against the St. Louis Blues.