I am surprised at the amount of players that used to play singles now play doubles and have become hugely successful at it. A few that spur to mind is Lee Yong Dae, Joachim fischer nielson,and Cai Yun. Looking at it the other way around have their ever been famous players that we know today that have started out playing doubles and have transitioned over to playing singles?
Park Joo Bong. Can't think of any other. BTW Ng Ka Long is concentrating exclusively on singles although he was ex World Junior Champion in doubles like Peter Gade and I think a couple of China female players.
You will notice Park Joo Bong's name is missing for a couple of times between his men's doubles World Championships. That time he was playing singles - even got seeded for the All England.
Yes, Ng follows from others who won WJC in doubles and then concentrated on singles. Other players who did that were Xie Xingfang and Park Sung Hwan. The two Parks were always good singles players, though. Park Sung Hwan won the AJC boys' singles title before he won WJC. Park Joo Bong went many years into his senior career as one of the go-to men for singles in the Thomas Cup, even though he was focussing on doubles generally. I think a lot of players played both as juniors and might have posted some doubles results but then focussed on just singles as seniors but I can't think of a senior doubles specialist who switched.
It was easier back in the days to compete at the highest level in multiple categories. There was an swedish player Thomas Kihlström in 70-80ies who got WC medals in singles, doubles and mixed.
