Mossavat began his professional career in 1990 being drafted by the Winnipeg Fury of the Canadian Soccer League. He was traded to Kitchener Kickers in 1990, and was transferred to the North York Rockets in 1992. After the demise of the CSL, North York joined the Canadian National Soccer League in 1993, and won the regular season championship. The following year North York joined the American Professional Soccer League, and as result Mossavat remained in the CNSL signing with league giants Toronto Italia. He made his debut for the club on May 29, 1995 in a match against the Hamilton White Eagles. During the season he was selected to the CNSL all-star squad which faced Parma F.C. on August 13, 1995. Mossavat concluded the season with Italia by finishing third in the standings. The next year he signed with St. Catharines Wolves, and with them he finished second in the standings, and reached the postseason finals where they were defeated by his former club Toronto Italia. He managed to achieve a Umbro Cup with St. Catharines finishing first in the Cup standings. Midway through the CNSL 1997 season, Mossavat was signed by the newly expansion franchise the Toronto Lynxof the USL A-League. He made his debut for the club on July 27, 1997 in a match against division rivals the Montreal Impact. Mossavat assisted the club in qualifying for the post seasonfor the first time in the franchise's history, by finishing 4th in the Northeastern division. The Lynx were eliminated in the first round of the playoffs against the Montreal Impact. The next year he signed with the Toronto Olympians of the newly formed Canadian Professional Soccer League. Throughout the 1998 CPSL season, he achieved an undefeated streak with the Olympians the first club within the league to achieve this milestone. As well as winning the double by winning the regular season and the Open Canada Cup. The club reached the playoff finals but where defeated by the St. Catharines Wolves by 4-2 victory in a penalty shootout. He re-signed with the Olympians the following season where he contributed in the club's second consecutive undefeated season which allowed them to claim the regular season championship; the first club to reach that milestone in the league's history. Within that year he managed to win a Treble with the club by claiming the Open Canada Cup, CPSL Championship, and the League championship. During the 2000 season, Mossavat was again instrumental in Toronto's exceptionally successful campaign where he led the Olympians to a 10-game undefeated streak, as well as claiming the Open Canada Cup in the process. The victory in claiming the Open Cup marked the first time in the league's history a club winning the trophy three consecutive years in a row. Though he did manage to lead his team to the playoff finals, they were defeated by Toronto Croatia by a score of 2-1. In 2001, he signed with the Toronto Supra where he reached the postseason by finishing third in the standings. After the 2002 season he retired from professional soccer, but he would eventually return to the Supra in a match on September 4, 2006 against the Italia Shooters. In 2007, Mossavat signed with the North York Astros making his debut on July 15, 2007 against the Italia Shooters.
Indoor career
Mossavat began his indoor career in 1995 with Canton Invaders in the National Professional Soccer League. The following season he signed with the Toronto Shooting Stars and appeared in 28 matches and recorded two goals. His next stint was in 1997 where he spent time with the Montreal Impact, and Milwaukee Wave.
