BOSTON (AP) -- It was a typical outing for Ervin Santana, shaky in the first inning and sharp the rest of the way.
For his third straight start, Santana allowed runs in the opening inning then found his rhythm as the Kansas City Royals ended Boston's seven-game winning streak with a 4-2 win over the Red Sox in the opener of a day-night doubleheader on Sunday.
''Once he gets settled in he gets on a nice roll,'' Royals manager Ned Yost said.
The nightcap was scheduled after Friday night's game was postponed because of the manhunt for a suspect in the Boston Marathon bombings.
Santana (2-1) allowed two runs on six hits with no walks and seven strikeouts. In his last three starts, he gave up four runs and nine hits in the first inning - then one run on 12 hits in his other 20.
''I was leaving a couple of pitches up in the first inning,'' Santana said. ''I feel comfortable every time I take the mound and I have confidence.''
The Red Sox loaded the bases with two outs in the eighth against Bruce Chen and Aaron Crow, but Jarrod Saltalamacchia grounded out to Crow. Greg Holland pitched a perfect ninth for his fourth save in five opportunities.
The Royals scored three runs in the fourth with Salvador Perez's two-run single breaking a 2-2 tie against Ryan Dempster (0-2), who had struck out the previous two batters.
''The difference in the game was Perez on the 1-1 slider for two runs as opposed to the eighth inning where we had the bases loaded and had a chance to create some damage,'' Boston manager John Farrell said.
Yost said Dempster made good pitches to Perez and the single ''wasn't a bullet by any stretch of the imagination. It was a ball that he could get just to the left of the shortstop into the outfield. Dempster made big pitches when he needed to, but Sal got the head of the bat and found some grass in the outfield.''
Still, Dempster felt he could have done better.
''I just didn't make a good enough pitch,'' he said. ''I had an open base. I just expanded the strike zone a little bit. I just didn't put it far enough out and gave him something good to hit.''
The atmosphere at Fenway Park was more like a typical baseball game following the emotional pregame ceremony when the Red Sox returned to action Saturday.
Still, there were some signs that all was not the same.
The American flag in left-center field remained at half-staff, Red Sox players wore a ''B STRONG'' patch on their jerseys and a fan held a white sheet with the words ''Veterans Luv Sox'' on it while ''God Bless America'' was sung during the seventh-inning stretch.
On his first two at bats, Jonny Gomes used a bat with the words ''Boston Strong'' and the names of the four people killed in the bombings and its aftermath on it. He popped out and grounded out.
Gomes planned to auction off the bats, which were suggested to him by his agent, Dan Lozano.
''He asked me if I was able to pull it off, would I be able to do it,'' Gomes said. ''He made it happen.''
The Royals took a 1-0 lead in the first on Alcides Escobar's second homer of the season. It didn't last long as the Red Sox scored twice in the bottom of the first when Daniel Nava and Dustin Pedroia singled, David Ortiz followed with an RBI single and Mike Napoli gave Boston a 2-1 lead with a run-scoring groundout.
After two hitless innings, Kansas City took a 4-2 lead in the fourth. Singles by Billy Butler and Eric Hosmer and an RBI-double by Lorenzo Cain tied the game with no outs. The threat started to fizzle when Dempster struck out Mike Moustakas and Jeff Francoeur. But then Perez singled past shortstop Stephen Drew.
That ended a season-opening streak of 16 games by Red Sox starters of allowing three runs or less, tying an AL record achieved by the Oakland Athletics in 1978 and 1981.
Notes: Red Sox RF Shane Victorino missed his first game of the season after leaving Saturday's 4-3 win over the Royals with back spasms. ... Pedroia has reached base in all 17 games. ... Jacoby Ellsbury has hit in 10 straight games. ... Cain had hits in seven straight at bats before grounding out on the first then getting his double in the fourth. ... The Royals recalled LHP Will Smith from Triple-A Omaha. ... Felix Doubront (1-0) pitches for the Red Sox against A.J. Griffin (2-0) in the opener of a three-game series with the Oakland Athletics on Monday night at Fenway Park. ... Kansas City is off Monday before starting a three-game series at Detroit on Tuesday night with Wade Davis (2-0) pitching for the Royals against Max Scherzer (1-0).