Krošlák initially celebrated successes on the second-rate Challenger Tour . He won two singles titles in his career. On the ATP Tour he collected a total of two titles in singles between 1995 and 1997 and was also in another final. In doubles he was also able to win a title with his compatriot Karol Kučera . In Grand Slam tournaments he reached the third round several times, but never got beyond it. He reached his highest single place in the world rankings on September 13, 1999 with position 53. In doubles he reached position 215 in June 1997.
In 1996 he took part in the Summer Olympics in Atlanta . He competed in both singles and doubles. In the singles he met the American MaliVai Washington in the opening round , to whom he was defeated in two sets. In the doubles competition he lost to the side of Karol Kučera to the British and later silver medalists Tim Henman and Neil Broad with 3: 6, 3: 6.
Krošlák played a total of 15 games for the Slovak Davis Cup team between 1994 and 2002 . Both his single record with 8: 4 wins and his double record with 8: 5 wins are positive. While Slovakia played in the Europe / Africa group zone III at the beginning of Krošlák's career, they had worked their way up to the world group by the end of his career.
In 2004 Ján Krošlák ended his professional career. Since then he has occasionally played in Challenger tournaments, most recently in Marburg in 2015 .
Slovakia
Tel Aviv
Javier Sánchez
Shanghai
Alexander Volkov
Ostrava
Andre Agassi
