 Christensen was originally drafted by the California Angels out of Troy High School in Fullerton, California in the 16th round of the 1978 MLB draft, but elected instead to attend California State University, Fullerton.The New York Mets then selected him in the second round of the 1981 MLB draft.After batting .313 at Triple-A Tidewater in 1984, he debuted with the Mets as a September call-up, batting .273 with three runs batted in and two runs scored with the big league club.