Ptacek played six years for the Saskatchewan Roughriders from 1960 through 1965, as a QB, LB and DB. Ptacek joined the Riders from the University of Michigan, where among other honours, he was named the outstanding player in the college All-Star vs. Pro game in 1959. Ptacek was drafted seventh by the Cleveland Browns of the NFL, but was traded to the Riders for tackle Jim Marshal. An ankle injury limited Ptacek to about half time in his rookie season with the Riders in 1960. Ptacek completed 99 of 178 passes for a 55.6% completion percentage and 1469 yards. In 1961, Ptacek was used mainly on defense, with only 52 pass attempts as Dave Grosz took ove the QB duties. Ptacek played linebacker, and rang up 3 interceptions in 1961 including one returned for a TD. Ptacek was named a West All-Star in 1961 at linebacker 1962, saw Ptacek return to the starting QB role, and he had his best season as a QB with 123 completions in 206 attempts for a very good 60.6% completion percentage and 2317 yards. Despite that excellent season, Ptacek was moved back to defense in 1963, and played defensive back almost exclusively for his final three seasons wit hthe Riders. The reason for the switch was simple. In 1963, the Western Riders swung a deal with the Eastern Riders to obtain a young QB by the name of Ron Lancaster. Ptacek had 3 interceptions in both 1963 and 1964, whiile being named a West All-Star at DB in 1964.

No official game participation stats were kept in the West until 1964.