Hosmer had just struck out when Bucknor pointed to the Royals' dugout and ejected Hosmer. Television replays then showed Hosmer shouting at Bucknor. Salvador Perez, who had the day off from catching, took over at first base.
Hosmer appeared to disagree with the first two strike calls in the at-bat. Hosmer also said later he was disturbed by a conversation Bucknor was having with Nationals catcher Wilson Ramos.
"As a hitter, you're going to get four at-bats a night, maybe even five," Hosmer said. "There's a reason we get here at 1 p.m., and prepare and watch videos, and do what we can to be ready for that guy tonight. It was obviously back-to-back calls I didn't agree with, but I realize it's a tough job back there. I realize it's not easy calling balls and strikes.
"But when something occurred before the inning and he decided to continue on with the conversation with the catcher, I just felt like his focus wasn't in there. I just felt like as a hitter and a competitor, you don't appreciate that."
Hosmer didn't say what that conversation was about.
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.