"Courier switched from Wilson to Donnay later in his career, he didn’t win any slams playing under Donnay."
What can we draw from this information?
If you’re starting out in tennis, or you’re a parent wanting to produce a Grand Slam champion, make sure you use Wilson rackets, you have a much higher chance of winning a Grand Slam.
..you scratch your head, you roll your eyes and move on.. and try really hard not to mutter an obscenity..