From 1971 to 1975, Tony DeThomasis was both an interuniversity wrestler and a member of the Yeomen rugby side. In rugby, he demonstrated his flexibility, speed and strength by playing three different positions: hooker, wing forward and prop. He played a key role in York's OUAA championships in both 1973-74 and 1975-76. During four seasons as a wrestler, DeThomasis recorded a first, a second and two third-place finishes in his 177lbs. category at the OUAA championships, twice qualifying for the national finals. His greatest achievement was in 1972-73 when he won the OUAA title in his weight class, was named MVP of the meet, placed third at the CIAU championships and was named York's male athlete of the year.