Ferrer’s loss was his first in the second round at a major since the 2010 Australian Open.
He made the quarterfinals at the last 10 Slams, including being the 2013 French Open runner-up.
In his other 46 career Grand Slam appearances, Ferrer only lost once to a player ranked lower than Kuznetsov — No. 126 Kei Nishikori at the 2008 U.S. Open.
Kuznetsov, the boys’ champion at Wimbledon in 2009, got to the third round of a major for the first time. It was also his first victory over a top-10 player.
Ferrer, of Spain, was the seventh seed at Wimbledon.