BALTIMORE -- Reliever Joel Peralta served up the go-ahead grand slam to Chris Gomez in the sixth and the Kansas City Royals' losing streak stretched to four games with a 6-4 loss to the Baltimore Orioles on Saturday night.
Royals starter Odalis Perez weathered five-plus innings in rainy conditions, but couldn't protect a 4-1 lead. Perez surrendered four runs on nine hits, walked one and struck out two.
Peralta (0-1) replaced Perez, who was yanked after giving up a single to Miguel Tejada and walking Aubrey Huff to lead off the sixth. Kevin Millar's single -- a pop fly to short left-center that shortstop Tony Pena called for but couldn't catch -- loaded the bases before Gomez ripped a 3-1 pitch into the left-field seats for his second career slam.
Scott Williamson (1-0) pitched a scoreless sixth for the victory.
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 David DeJesus in the right foot to lead off the game and singles by Mark Grudzielanek and Mark Teahen loaded the bases. DeJesus crossed on Reggie Sanders' double-play grounder before an Ross Gload's infield single scored Grudzielanek.
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.