Reliever Joel Peralta served up the go-ahead grand slam to Chris Gomez in the sixth and the Royals' losing streak stretched to a season-high four games with a 6-4 loss to the Baltimore Orioles in a game played in a steady downpour.
Peralta, who relieved Odalis Perez with two on and none out in the sixth, was put in a precarious situation after Pena was unable to grab Kevin Millar's flare to short left-center. That loaded the bases for Gomez, who worked to a 3-1 hitter's count before ripping a fastball into the left-field stands for his second career grand slam.
Pena made a dead run from short, his back to the infield, before pulling up at the end of the play, as if he expected an outfielder to wave him off. Even though Reggie Sanders was charging hard from left and David DeJesus was running in from center, Pena inexplicably took control instead of the center fielder. Pena got some leather on the looper, but the ball bounced off his glove and the Royals lost a chance to end a three-game slide.
"The center fielder, in my eyes, has a better chance at that ball," manager Buddy Bell said. "He's going way out in no man's land. When an infielder goes out that far, an alarm clock goes off in your head and you say, 'I'm out here way too far,' and that's when that play gets messed up."
Pena stayed with the play because he didn't think DeJesus, the closer of the two outfielders in pursuit, had a chance to catch the ball.
"It just landed in the middle of nowhere," Pena explained. "David didn't have a chance for it, and me, I just dropped it. (Millar) couldn't have placed it better if he'd tried. (It's) the way things are going right now."
DeJesus said he didn't so much call Pena off, just warned him that he was going to have a clear route to the ball instead of dodging sliding outfielders.
"Obviously, it's going to be easier for someone coming in," DeJesus said. "But it's one of those things that we weren't close enough to the ball. Tony, I thought, had a better play towards it than we did."
By the time the ball bounced to the soggy turf in left-center, the damage was done, and another self-fulfilling prophecy was unfolding for the snakebitten Royals, who have lost seven of eight and fell to 1-5 on their first road trip of the year.
"When that happens, it's a totally different situation," Bell said. "Rather than runners on first and second with one out, it's bases loaded with nobody out. Now the way you pitch, the way you play, is totally different. That was the key play of the game, no doubt about it."
The thin margin for error grew even smaller when Peralta (0-1) went to 3-1 on Gomez.
"I fell behind the hitter and he got me. That was the game right there," Peralta said.
Scott Williamson (1-0) pitched a scoreless sixth for the victory as the Orioles won their third straight. Chris Ray worked the ninth for his third save. Baltimore can close out its first four-game sweep of the Royals since May 2-5, 2002 at Camden Yards.
Baltimore's comeback from a 4-1 deficit ruined a gutsy effort by Perez, who pitched five-plus innings in a steady drizzle but couldn't hold a lead. Perez surrendered four runs on nine hits, walked one and struck out two.
"We had some momentum going in our favor," Bell said. "Odalis made some good pitches when he had to, we got some double plays, he got some key outs when he had to.
The Royals, who had scored only one run in losses in the first two games of the four-game series, matched that total in the first inning against right-hander Daniel Cabrera.
Cabrera hit DeJesus in the right foot to lead off the game and singles by Mark Grudzielanek and Mark Teahen loaded the bases. DeJesus crossed on Sanders' double-play grounder before Ross Gload's infield single scored Grudzielanek to make it 2-0.
Sanders scored on a passed ball by catcher Paul Bako in the third and Sanders drove in a run on a fielder's choice for a 4-1 lead in the fifth.
Pete Kerzel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.