Friday's victory, the O's third in as many tries against the Royals this year, was highlighted by six scoreless innings from Hammel and a five-run fifth inning that chased Royals lefty Bruce Chen, as Baltimore improved to 22-1 when getting a quality start and 5-0 following an off-day.
The O's early offense -- which ended with all nine starters reaching base safely -- helped the surprising first-place club continue to prove that they belong atop the American League East.
How exactly are the O's, picked by many to finish in the division's cellar, doing it? They are getting contributions from everywhere.
The Orioles, winners of 21 of their last 31, have secured their third consecutive winning month -- dating to last September -- for the first time since September 2004 to May 2005. They are an AL-best 29-17, with a Major League-leading 68 home runs -- including Chris Davis' two-run seventh-inning shot -- and sport a 2.38 bullpen ERA that entered Friday as the second-best in baseball.
Even the crowd is in uncharted territory with the 28,954 assembled at Camden Yards featuring nearly 11,000 walk-up tickets purchased, a new stadium record.
"They're engaged and it was a good atmosphere," manager Buck Showalter said of the loud and lively bunch that came out to kick off Memorial Day weekend. "And we've got to keep doing the things that make it continue. My first thought in the dugout was, what was the [stadium] promotion? You want the promotion to be good baseball."
There were fireworks after the game and discounted student seats, but neither promotion was likely unique enough to account for the walk-up crowd.
Hammel did his part to put on a good show, striking out seven and pitching six full innings for the first time since admitting to right knee soreness that caused him to miss a start. The 29-year-old Hammel battled all night, but got the big "K" when necessary, using a lethal four-pitch mix to keep Kansas City off the scoreboard.
"He threw the ball well," Royals manager Ned Yost said of Hammel, who improved to 6-1 with a 2.78 ERA since joining the Orioles. "His stuff is better than what I remember in Colorado. It surprised me a little bit. We saw it on video, but I wanted to see it in person. I was impressed."
So was Showalter, who praised both Hammel's command and crispness of his pitches, compliments the right-hander didn't dole out so easily.
"Honestly I think I had a good mix of being effectively wild and bearing down when I needed to tonight," Hammel said of the 104-pitch outing in which he was charged with five hits and a walk. "Obviously J.J. [Hardy came up] with a great play up the middle tonight on the line drive to [retire Billy] Butler, and then a big inning for us. It was the perfect storm."
Hardy's fifth-inning defensive wizardry at short was also a huge momentum shift, allowing Hammel to get out of his second jam of the night unscathed and allowing the Orioles' offense time to respond with a five-run frame.
After giving up a one-out single to Alcides Escobar, that just eluded a diving Nick Markakis, Hammel's own throwing error on Jarrod Dyson's single put runners on the corners with one out. Dyson stole second and Butler smoked a line drive that Hardy leaped up for and caught for an inning-ending play.
"I caught it in the palm," Hardy said of the screaming liner. "It really hurt. I think maybe I jumped higher than I thought I could. Maybe I didn't need to jump that high, but I hurt my hand."
"I don't know who jumped higher, him or [Hammel]," Showalter said. "Billy Butler is one of the better right-handed hitters in the league. He's a tough out and he squares us up a lot. We dodged a bullet there."
Hardy also came up big in the bottom of that frame, connecting for a two-run double off the right-field scoreboard to start the team's rally and send Chen to an early exit. Xavier Avery worked a leadoff walk and stole second, advancing to third on Robert Andino's textbook bunt that died on the infield grass for a hit.
Andino also proceeded to steal second, masterfully working around Escobar's tag -- which completely missed Andino's outstretched hand -- to put a pair of runners in scoring position.
"Momentum's a big thing in this game," Hardy said when asked about the lift the pair of stolen bases gave the O's dugout. "Had one of them been thrown out at second, it could have been a total momentum changer. It was first and third when Dino put the swim move on there, and got in there. It could have gone totally different."
But, like seemingly everything right now, it went the Orioles' way. Hardy drove them in and Markakis followed with his own RBI double to push the Orioles' lead to four. Adam Jones, who got the O's on the board with a first-inning sacrifice fly, delivered an RBI single, and two outs later, Davis drove in the inning's final run.
Davis crushed a ball from reliever Louis Coleman two outs into the seventh inning, giving the Orioles six players with seven or more homers this season.
Reliever Stu Pomeranz, who was recalled from Triple-A prior to the game, followed Hammel and allowed a two-run homer to Jeff Francoeur in the eighth. Those were the first earned runs allowed by Pomeranz, who has played at three different levels this season.