When a true professional tour was at last started, Koželuh was one of the first players to join it, being signed up for it by Vinnie Richards, who made a special trip to Europe for that sole purpose. In the years to come Koželuh would achieve much greater prominence as a pro than as an amateur. In 1928, his first year as a professional, he beat Richards 15 matches to 5, at a time when Richards was generally considered to be one of the 5 or 6 best players in the world, amateur or professional. In the following years Koželuh continued to dominate Richards, in 1929 beating him 5 times to 2 and in 1930 4 times to 2. After watching one of their lengthy matches, a tennis expert of the time, J. Parmly Paret, wrote in American Lawn Tennis, that Koželuh had "the most perfect defense that I have seen... But defense alone does not make a champion." He went on to say that either Henri Cochet or Bill Tilden at their best would be able to defeat Koželuh by attacking him consistently from the net. Koželuh defended his somewhat tedious baseline style by saying: "Why should I change my style when it is so successful?"