Neville E. Guard-USA TODAY Sports

Brent Rooker hit Dylan Coleman's fourth pitch of the ninth inning for a two-run, walk-off home run Monday night, delivering the Oakland Athletics a 6-4 victory over the visiting Kansas City Royals in the opener of a three-game series.

In a duel of the teams with the worst records in baseball, the A's (35-90) beat the Royals (40-87) for the third time in four meetings this season.

After the Royals rallied from a two-run deficit to tie the game in the eighth, Coleman (0-2) hit Ryan Noda with his first pitch of the bottom of the ninth. Two balls later, Rooker connected with Coleman's first strike, bombing his 21st homer of the year over the wall in left-center field.

A's closer Trevor May (4-4), who worked a 1-2-3 top of the ninth with two strikeouts to preserve a 4-4 tie, earned the win.

Powered by six strong innings from Paul Blackburn and solo home runs by Jordan Diaz, Zack Gelof and Shea Langeliers, the A's took a 4-2 lead into the eighth before the Royals rallied to pull even.

Pinch hitter Matt Beaty ignited the two-run comeback with a leadoff double, and Kyle Isbel walked. Maikel Garcia made it 4-3 with a sacrifice fly, after which Michael Massey tied the game with a two-out RBI single.

The homer by Diaz, his ninth, came against the Royals' first reliever, Taylor Hearn, in the second. Gelof connected for his ninth in the third and Langeliers his 12th in the sixth, both off Alec Marsh.

Seth Brown hit an RBI single for the A's in the fifth, while the Royals' first two runs were the products of a Freddy Fermin sacrifice fly in the second and a Bobby Witt Jr. home run, his 25th, in the sixth.

Blackburn left with a 4-2 lead, having limited the Royals to four hits and one walk. He struck out six.

Marsh worked 5 2/3 innings for the Royals. He allowed three runs and five hits with one walk and nine strikeouts.

Noda reached base four times via a single, two walks and the ninth-inning hit by pitch and scored twice for the A's, who were coming off a three-game home sweep at the hands of the Baltimore Orioles. Lawrence Butler added two singles for the A's, who out-hit the visitors 10-6.

MJ Melendez tripled and scored a run for the Royals, who lost for the sixth time in seven games.

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