Leonard first announced his talent when he set a new Cuban 100 m national junior record in 1973 with a time of 10.24 s. Leonard was successful in the 1974 Central American and Caribbean Games winning the 100 and 200 m double. He came to the attention of the world when he equalled the then world record for a 100 m with a hand-timing of 9.9 s on 5 June 1975 in Ostrava.[note 1]
Leonard was three-time Pan American Games champion, 1975 100 and 1979 100/200. When winning the title in 1975 he suffered a calamity that could seem comical if it were not for the fact that the outcome for Leonard could have been even worse. Whilst celebrating his win, he fell into the moat around the track. The injury he suffered to his back required surgery and severely hampered his preparations for the 1976 Olympics. In the race itself, Leonard defeated the Trinidadian Hasely Crawford who was to win the Olympic 100 m title the following year.
Leonard did recover in time to compete at the 1976 Montreal OLympics but there suffered another misfortune. He cut his left leg on broken glass in the Olympic Village. The injury badly affected his running and he was eliminated in the quarter-finals.
In 1977, Leonard was at the peak of his powers. He became the second athlete to run the 100 metres in less than 10 seconds with electronic timing, running in 9.98 s on August 11 in Guadalajara (the first was 1968 Olympic champion Jim Hines). Leonard also had good speed endurance which he proved when he was the fastest in the world that year in the 200 metres with a time of 20.08 s. At the inaugural Athletics World Cup that year, Leonard won bronze in both the 100 and 200 m whilst representing the Americas. On 13 September he set a low-altitude world best time for the 100 m at 10.03 s.[note 2] He also won the 1977 100-metre Gold at the World Student Games.
In 1978 he successfully defended his double Golds in the 100/200 m at the Central American and Caribbean Games. He also set a personal best and world's fastest time at the 200 m of 20.06 s on 19 June in Warsaw.
In 1979, at the second Athletics World Cup he won the 200 m and was runner-up in the 100 m. He was also Cuban champion and won the Soviet 100 metre championship that year.
At the 1980 Summer Olympics Leonard won a silver medal in 100 metres, finishing behind Allan Wells of Great Britain. He then went on to finish 4th in the Olympic 200 metre final in a time of 20.30, narrowly missing out on another medal.
Leonard was never a factor at world level after the 1980 season and disappointingly there has been no legacy of world-class Cuban sprinters to follow him and his 100 and 200 m bests are still Cuban records.[note 3]
He retired in 1985 and is reportedly now a track coach.
^From 1 January 1977, imperial distances were no longer recognised for world-record purposes by the IAAF.
^The IAAF world records take no account of altitude of the record's venue. However, as it is recognised that sprint events are assisted by altitude, due to decreased air resistance, a separate list is kept of best marks at sea-level when they are inferior to the actual world record.
Leonard was ranked among the best in the world in both the 100 and 200 m sprint events over the incredible spread of 8 seasons from 1973 to 1980, according to the votes of the experts of Track and Field News.