Matched against Kansas City's hard-throwing Tim Collins, Dunn went to the opposite field for his 35th homer this season and the 400th of his career. Dunn joins Paul Konerko as the only teammates in Major League history to reach 400 homers in the same season. Konerko hit his 400th on April 25, at Oakland.
Dunn's blast came immediately after Kevin Youkilis recorded the 1,000th hit of his career. Dunn has eight seasons with 30-plus homers, which ranks fourth among active players behind Alex Rodriguez, Jim Thome and Albert Pujols.
It was a bittersweet accomplishment, though, as it came in a 9-4 loss.
"It's hard to enjoy," said Dunn. "Obviously, I wish it had come in a win."
Robert Falkoff is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.