BALTIMORE -- The Orioles had hoped to use a four-game series against the Boston Red Sox as a measuring stick to see if they could compete with a powerfully built team that relies on solid pitching, clutch hitting and strong defense. Three games into the assessment, there are numerous unanswered questions, certainly more than manager Dave Trembley would prefer to be facing.

Needing a deep start to protect an overworked bullpen, the Orioles instead got only four ineffective innings from Brian Burres on Sunday and lost, 9-4, to the Red Sox.

By dropping their fourth straight game and falling three games under .500 for the first time this season, the Orioles are putting themselves in a precarious situation entering the final game of the weekend wraparound series. After the Red Sox and their vociferous fans depart, Baltimore embarks on a stretch of 18 of 24 games on the road.

"We lost three games. It happens," second baseman Brian Roberts said. "Certainly, today didn't go as well as we'd have liked. ... They played good for three days. We didn't play that bad the first night, and we didn't play that bad last night."

Sunday? The Red Sox were head and shoulders above the O's at every turn. On Monday, Boston will try to complete its first four-game sweep in Baltimore since Sept. 20-23, 2002.

"The three things we were looking for, Boston got," Trembley lamented. "They got a very good start out of [Bartolo] Colon. They got outstanding defense. They made every play. And they got timely hitting. That was the story of the game."

Colon (3-0) is unbeaten in three starts since being recalled from Triple-A Pawtucket on May 21. He went six-plus innings, giving up four runs on seven hits, walking two and fanning five.

"He had the two-seamer going and he hit his spots," Orioles center fielder Adam Jones said. "He had good defense behind him and he basically pounded the zone."

Burres (4-5), by contrast, allowed seven runs on 12 hits, walked one and struck out two. It was the second consecutive rough outing for the left-hander, who got a no-decision when he gave up eight runs and 10 hits in 3 2/3 innings against the New York Yankees on Tuesday. He has one victory in his past seven starts.

"Unfortunately, our expectation was that Burres was going to give us a better start," Trembley said. "It didn't happen. They look like they're really in a groove swinging the bat, and obviously they were helped by great defense in the field."

After a three-run Red Sox third put the Orioles in a 4-1 hole, Burres surrendered consecutive home runs to Manny Ramirez and Mike Lowell to make it 7-1 in the fourth. Ramirez followed Kevin Youkilis' fielder's choice grounder with the 501st homer of his career, a drive to right-center field, and Lowell hit a solo shot inside the left-field foul pole.

"I really just pitched behind a lot and didn't locate down. I got a lot of balls up and they swung it pretty well," Burres said. "When I did make a bad pitch, they didn't miss it. Even a couple of good pitches got hit. It was just one of those days I have to try to learn from."

Added Trembley: "[Burres] didn't pitch down, is what he didn't do. Everything was up. He looked like, on his changeup, he was really slowing down; they had an awful lot of deep counts. Heck, he had 75 pitches in the third inning. Obviously, they were seeing it really good, fighting it off, fighting it off, fighting it off."

The Orioles, handcuffed by Colon, did benefit from Luke Scott's seventh homer of the year, a two-run blast off the top of the right-field scoreboard, cutting the deficit to 7-3 in the fourth. Otherwise, it was a struggle, as the Red Sox continued pour it on.

J.D. Drew also homered for Boston, connecting in the seventh off Steve Trachsel, who was making only the second relief appearance of his 16-year Major League career and the first since June 6, 1995, with the Chicago Cubs. Later in the inning, Jacoby Ellsbury hit a two-out RBI single for a 9-3 lead.

Trachsel, whose relief appearance took him out of contention for a Tuesday start in Minnesota, had not pitched since May 24. Although the right-hander lowered his ERA from 8.82 to 8.15, he didn't know if he would remain a bullpen option.

"I don't. I really don't. If it's [relieving], as long as I know, because I'm all about preparation," Trachsel said. "If I can prepare and know what to prepare for, I don't see any reason why I can't be successful at doing whatever role they want."

While Trachsel's effort took some pressure of the bullpen, the Orioles' bats didn't come alive, as Trembley had hoped. Time and again, Boston's defense stiffened. Second baseman Dustin Pedroia made several nice stops up the middle and right fielder J.D. Drew made a fully extended grab of Scott's sinking liner in right-center to end a two-on, two-out threat in the seventh.

"You're probably going to win games if you play defense half that well," said Roberts. "It's one of those days. I don't know -- if any team makes those plays, the other team's probably going to lose. You tip your hat and you move on."

"You hit a bump in the road and you keep plugging along," Roberts added. "Every team hits them at some point. There's still a long ways to go and you keep battling."