Aaron Cook had a no-hitter through 5 1/3 innings, but fell apart after that. (AP)

BALTIMORE — For a second straight night, things fell apart in a hurry for the Red Sox. This time it resulted in a 5-3 loss to the Orioles Wednesday night at Camden Yards.

The defeat put the Red Sox at four games under .500 (57-61) for the first time since May 13.

After Red Sox starter Aaron Cook made it through the first 5 1/3 innings without giving up a hit, the Orioles exploded in the sixth, scoring five runs while batting around in the order. Cook finished having surrendered five runs on three hits, walking three and striking out a batter. He was followed in the sixth by relievers Andrew Miller, Junichi Tazawa and Craig Breslow.

Here is what went wrong (and right) for the Red Sox:

WHAT WENT WRONG

- Baltimore’s J.J. Hardy broke up Cook’s no-hitter with one out in the sixth inning with a line-drive single to left field. Up until that point, the righty had only thrown 61 pitches, while getting 13 of his 14 outs on ground-outs. The next batter, Nate McLouth, rifled a single to center field to plate Nick Markakis (who had walked) with the host’s first run.

- Cook made a costly miscue in the sixth, when he gathered in Adam Jones’ grounder back to the mound and sailed the potential 1-6-3, inning-ending double play into center field. The error allowed the Orioles to tie the game at 2-2, as Hardy scores. That led to Matt Wieters’ ground-rule double, giving the O’s a one-run lead.

- After not quite being able to get over to Wieters’ double, Red Sox left fielder Carl Crawford just missed reaching Mark Reynolds’ line-drive into the left field corner. The double — which came against reliever Junichi Tazawa —  resulted in two more runs for the Orioles, boosting their lead to 5-2.

- Both Adrian Gonzalez and Bobby Valentine were ejected by home plate umpire Mike Everitt with one out in the eighth inning after Gonzalez complained about a strike call prior to grounding out to second base. It was Gonzalez’ second career ejection, and Valentine’s 41st. The Sox manager has been ejected four times this season.

WHAT WENT RIGHT

- Jacoby Ellsbury continued his historic streak against the Orioles, making it 38 straight games he has notched at least one hit against Baltimore. According to Elias, the streak is the second-longest since 1900 for any player against another team, only trailing Vlad Guerrero’s streak of 44 games vs. Texas. Ellsbury kept the streak alive by claiming a ground-rule double to center field in the fifth inning, scoring Scott Podsednik with the game’s first run.

- The Red Sox would increase their lead to 2-0 with another run in the fifth, this one coming courtesy Carl Crawford’s sacrifice fly, scoring Nick Punto. Punto would also score the Sox’ third run, coming in on a Crawford ground-out in the seventh to cut the Orioles’ lead to two runs.

- Red Sox catcher Jarrod Saltalamacchia absorbed a vicious collision with Adam Jones in the sixth inning, taking a throw from second baseman Dustin Pedroia (who was playing in) on Chris Davis’ grounder. The play kept the Red Sox within a run at the time.