Salvador Perez hit a go-ahead two-run single in the top of the fourth inning to help the Kansas City Royals beat the Boston Red Sox, 4-2, in the opener of a day-night doubleheader at Fenway Park.
Kansas City starter Ervin Santana (2-1) gave up two first-inning runs, but kept the Red Sox off the board through the remainder of his outing, retiring 11 in a row at one point.
"Once he gets settled in he gets on a nice roll," Royals manager Ned Yost said.
Santana scattered six hits and struck out seven over seven frames.
David Ortiz went 3-for-4 with an RBI for Boston, which had its winning streak snapped at seven games.
Red Sox starter Ryan Dempster (0-2) allowed four runs on six hits, walked three and fanned eight in seven innings.
Boston threatened in the eighth against the Kansas City bullpen, notching two hits against Bruce Chen. Aaron Crow then issued a two-out walk to Mike Napoli to load the bases, but Jarrod Saltalamacchia was retired on a grounder back to the pitcher.
Greg Holland earned his fourth save of the season with a flawless ninth.
Alcides Escobar hit a solo home run over the Green Monster in the first inning, but the Red Sox quickly responded during their half of the frame.
Boston strung together three straight one-out singles, with Ortiz driving home Daniel Nava. Dustin Pedroia then scored on Napoli's grounder to second.
Lorenzo Cain's RBI double, one of three consecutive Kansas City hits to open the fourth, tied the game. After the next two batters struck out, Perez delivered with a liner into left-center field.
"The difference in the game was Perez on the 1-1 slider for two runs," Red Sox manager John Farrell said.
Red Sox starters had allowed three or fewer runs in each of the first 16 games this season ... Boston center fielder Jacoby Ellsbury extended his hitting streak to 10 games with a single in the second.