Mendel began his musical career in the hardcore band Diddly Squat, which only recorded a 7" single but did a national tour during the 1988 summer vacation. After Diddly Squat ended, Mendel moved to Seattle, where he spent four months on the straight edge band Brotherhood. Afterward, he joined the band Christ on a Crutch, which included bandmate Glen Essary and lasted until 1993. In 1992, Mendel and his University of Washington housemate Dan Hoerner decided to form a band, and invited drummer William Goldsmith to form the group that would end up being named Sunny Day Real Estate (SDRE). Mendel added that SDRE was an attempt to "play more intricate, interesting music". While Mendel toured Europe with Christ on a Crutch, Jeremy Enigk jammed with the remaining members and eventually became a full-time member of SDRE.