Gavin Floyd's one bad inning was too much for the Chicago White Sox to overcome.

Floyd allowed five runs in the fifth inning while Zach Britton pitched six strong innings and Nick Markakis hit a three-run double to lead the Baltimore Orioles to a 6-4 victory Sunday.

"In one inning all of a sudden, he lost it," White Sox manager Ozzie Guillen said. "And they take advantage of it. Gavin just had one bad inning. It was a very nice first couple of innings."

The White Sox made things interesting in the ninth, putting the first two runners on base against Baltimore closer Kevin Gregg. But Paul Konerko and Alex Rios were called out on strikes, and A.J. Pierzynski grounded out to second to end the game, sending the Sox to their 15th loss in 18 games. They also left 11 men on base.

Rios was ejected by plate umpire Cory Blaser for arguing his call.

"Just because you go out and play hard doesn't mean you're going to win or get the hit," Konerko said. "But over the long haul, you've got to believe you will. I believe I will and I believe the team will."

Luke Scott hit his fifth home run off Floyd (3-2) in the fourth inning on a 1-2 pitch to give the Orioles a 1-0 lead. But for Floyd, the real trouble began the following inning.

Mark Reynolds started the inning with a solo homer, his third of the year, to the bleachers in left-center, making it 2-0.

After a triple by Felix Pie and back-to-back walks to Robert Andino and Brian Roberts loaded the bases, Markakis cleared them with a three-run double, stretching the lead to 5-0.

"They put a couple of people on base and they had the big hits," Guillen said. "They did it yesterday, they did it the night before, they did it today. I think we got good at-bats late in the game. We just came up short."

Scott added another RBI later in the inning on a two-out single to make it 6-0. He finished 2-for-4 with two RBIs. The first five batters of the inning all reached base and scored.

Floyd pitched six innings, allowing six earned runs on seven hits. He struck out five.

"I got behind," Floyd said. "Getting behind guys is definitely not the way to go. I was pretty good for four innings, then I lost it a little in the fifth."

Adam Dunn came in as a pinch-hitter in the eighth inning and connected on a two-run homer, his third of the season, which cut the lead to 6-4.

But the White Sox mustered little offense early against Britton (5-1). The 23-year old rookie, making his sixth career start, pitched six innings, giving up one run and scattered five hits, lowering his ERA to 2.63. Britton said after the game he was pitching with a callus on his left middle finger.

"It all comes back to having confidence in my defense," Britton said. "I didn't have my good stuff, but I just threw it over the plate and let them hit to the guys and let them make the plays."

Brent Lillibridge got the White Sox on the board in the bottom of the fifth, leading off the inning with his third homer of the season, making it 6-1.

Gordon Beckham led off the seventh inning with a double that got past a diving Pie in center field. Juan Pierre and Alexei Ramirez drew back-to-back walks to load the bases with one out, but the Sox only scored once. Carlos Quentin popped out, Konerko drew a bases-loaded walk, and Rios grounded out to end the threat.

"We had a chance to win it in the ninth," Beckham said. "We didn't let that game get away from us. It took us some innings to get going, but once we did, that's the way we can play."

Konerko and Beckham were each 2 for 3, and Pierre reached base four times.

Notes: Vladimir Guerrero went 1 for 4 in the game. He has not drawn a walk in 108 plate appearances this season. ... Britton's four wins in April set an Orioles franchise record for victories in April by a rookie. ... The White Sox finished April nine games out of first place, their largest division deficit after the first month of the season since 2001. Their 18 April losses were also a franchise record. ... Floyd has pitched at least six innings in all six of his starts this season. ... Orioles SS J.J. Hardy, on the 15-day DL with a strained left oblique, is scheduled to take batting practice in the cages Monday and Tuesday, then on the field Wednesday. ... White Sox left-handed hitters Pierzynski and Dunn were not in the starting lineup against Britton.