Nusslein was banned from the amateurs. He was found guilty of accepting gifts and money by the German Tennis Federation, who said that it was tantamount to turning professional. Nusslein had no choice but to play tennis professionally if he wanted to play tennis competitions. I don't know if Nusslein ever even played a match as an amateur. And as I've already pointed out, Nusslein won Roland Garros twice as a professional in the French Pro. Best clay-court player of the 1930s, most probably. Although Gonzales turned professional at age 21, he had already had 3 years as an amateur before this. And Segura, while being a good player as an amateur (reaching 4 US Championships semi finals in a row from 1942-1945, and the quarters in 1946 and 1947), he really came into his own a few years into his professional career (around 1950). When Segura turned professional in late 1947, Kramer (Wimbledon and US Championships holder) and Pails (Australian Championships holder) also turned professional. Kramer was to challenge the world's best professional player, Riggs, and Pails and Segura were to play against each other on the undercard of the tour. Pails won the tour 41-31, so Segura didn't have the quickest start early on in his professional career. As I said, it was around 1950 that he went up several levels, winning the US Pro (the first of 3 in a row on different surfaces) and becoming the second best player in the world behind Kramer. Segura also did a lot better on the 1951 world pro tour against Kramer than what Gonzales had managed the previous year. And Segura was better than Olmedo in 1960, as the world pro tour showed.