That's an interesting point. In 2013, Sina interviewed Waldner. When asked who he had the most difficulty playing and who he admired the most among all the players he's played, he answered...
http://sports.sina.com.cn/o/2013-09-27/16336803953.shtml
Question: I would like to ask Lao Wa, among the Chinese players you have played with, who do you admire the most?
Waldner: Zhang Jike.
...
Question: Mr. Lao Wa, here's my question. You've played with so many generations of Chinese players. Who do you think is the most difficult to play? Also, the 2 Grand Slam holders like you are now head coaches. Do you want to be a coach? I'm looking forward to seeing you again in the arena.
Waldner: Originally, Ma Lin and Liu Guoliang. There is currently no time for coaching. Because I still participate in leagues in Sweden. In addition, I have many other things to do, such as attending this stamp event in Beijing today. We also have a website
www.lao-wa.com, and many related matters also require me. When the national team coach needs more than 270 days of training time each year, I really can't take it.