Baseball statistician Bill James cited Phelps as an example of a player who is unfairly denied a chance to play in the majors, despite compiling strong minor league statistics.

[3] All this earned Phelps a chance from Coach Jim Brock to play at ASU, where he was named to the College World Series All Star team in 1976, when the Sun Devils lost to rival Arizona after having defeated the Wildcats seven times that season, including a first-round game in Omaha.

[5] On September 20, 1980, he made his major league debut against the Oakland Athletics, appearing as a defensive replacement in the seventh inning and grounding out in his only at bat.

[8] An average defensive player, Phelps was better suited to play with the Mariners, as he could serve as the designated hitter, and the struggling franchise also had plenty of room for advancement.

[2] Impressed, owner George Steinbrenner of the New York Yankees traded Triple-A prospect Jay Buhner to Seattle in exchange for Phelps,[16][17] despite already having Don Mattingly and Jack Clark to play first base and DH.

With limited playing time, Phelps found it difficult to maintain his production of the previous four-and-a-half seasons, while Buhner went on to become an All-Star and legendary Mariners player.

A Seinfeld episode in early 1996 ("The Caddy") depicted Yankee fan Frank Costanza (played by Jerry Stiller) as more upset about the Buhner trade than about the supposed death of his own son George.

Phelps was called out of the dugout to pinch hit against Brian Holman of the Mariners,[24] who had retired the first 26 batters in succession; he homered on the first pitch to ruin the perfect game.

[31] He has since done baseball analysis for Fox Sports, along with community and media work for the state's largest electric utility, Arizona Public Service.

Programs that Phelps has been involved with (The ABC's of Baseball, and Life and Power Players) have received national recognition for having positive impact on children.