cuellar made his major league debut with cincinnati in a 14–9 loss to the philadelphia phillies at crosley field on april 18, 1959. he entered the contest in relief of don newcombe in the second inning with the reds losing 4–2. in his two innings of work, cuellar surrendered a grand slam to gene freese in the third and a two-run double to al schroll in the fourth. his only other appearance with the reds came three days later in its 7–4 defeat to the milwaukee braves at county stadium on april 21. again he pitched two innings in relief, but he gave up two runs.