But the lefty began his professional career as a 19-year-old during the 1956-57 Cuban League season with Almendares. He pitched for the Scorpions during the final five seasons of the league, compiling a sub-.500 21-28 record despite a 3.09 ERA.
During the 1959-60 season, Cuellar went 5-10 desptie a stellar 2.92 ERA as Almendares won the Cuban League pennant and went on to win the Caribbean Series.
As a minor leaguer, Cuellar (second row, fourth from the left) played with the Havana Sugar Kings from 1957-60, registering ERAs of 2.44, 2.77, 2.80 and 3.53 in those seasons and was with the team when it was forced to move from Havana to Jersey City in the middle of the season after the International League -- in the wake Fidel Castro coming to power in 1959 -- revoked the franchise and gave Cuban owner Bobby Maduro 48 hours to find a city to which to transfer the team.
In the majors, Cuellar used his screwball to become the only Cuban-born pitcher to win the Cy Young Award in 1969 as he went 23-11 with a 2.38 ERA for the Orioles. He won 20 or more games four times, including 1971 when he joined Pat Dobson, Jim Palmer and Dave McNally as the Orioles' four 20-gamer winners that season.
Cuellar was inducted into the Cuban Baseball Hall of Fame in 1984.