Johnson had a rookie team-record 24 goals and tied with MacKinnon for the NHL lead among rookies. MacKinnon, selected first overall in the draft by Colorado, led all NHL rookies in scoring with 63 points.
Palat finished second among rookie scorers with 59 points and 23 goals.
The award winner will be announced June 24 at the NHL awards banquet in Las Vegas.
"It's pretty cool. It's always good going back to Vegas," MacKinnon said after Avalanche practice in Minnesota on Wednesday. "It's going to be fun. I watched it on TV growing up and things like that, but it's going to be fun to be with some of the guys I know."