Red Sox first baseman Kevin Youkilis follows his double against the Orioles in the first inning. (Rob Carr/Associated Press)

Saturday evening's showdown at Camden Yards in Baltimore had mismatch written all over it, beyond Boston's16½-game lead over the hometown Orioles.

Red Sox ace Jon Lester entered the game unbeaten in 13 career starts versus Baltimore, sporting a 10-0 record and 2.22 earned-run average.

The left-hander also had won six times in his previous eight outings and was coming off a month of May during which he went 5-0 with a 1.84 ERA and 45 strikeouts in 44 innings pitched to earn American League pitcher of the month honours.

Orioles righty Jeremy Guthrie, meanwhile, was looking for his first win over Boston in more than two years, and was backed by an offence that had scored just 14 runs in a nine-game losing stretch.

Make it as season-high 10 defeats as Baltimore's bullpen imploded in the ninth inning, coughing up six runs to turn a 2-0 game into an eventual 8-2 blowout, Boston's second win is as many nights after being swept in a three-game series at Camden Yards from April 30-May 2.

Darnell McDonald, Bill Hall and Kevin Youkilis each doubled home two runs in the ninth against Orioles relief pitchers David Hernandez, Will Ohman and Jason Berken to help the Red Sox keep pace with Toronto in the American League East. The Blue Jays outlasted the New York Yankees 3-2 in 14 innings earlier Saturday and are tied with the Sox for third in the AL East at 33-24.

Lester (7-2) helped Boston extend its road winning streak to seven games — something the Red Sox haven't done since June 2005 — and is 7-0 in his last nine trips to the mound, matching the longest undefeated run of his career.

3 walks in 7th

He breezed through the first six innings but appeared to tire in the seventh on a warm night in Maryland. Lester fanned Matt Wieters to open the bottom of the inning but proceeded to walk his first three batters of the night — Adam Jones, Garrett Atkins and Julio Lugo.

Fortunately for Lester and his teammates, fireballer Daniel Bard came on and retired the next two batters, getting Luke Scott to fly out to centre-field and Corey Patterson to pop out to Youkilis at third base.

"If we score some runs in that inning when we had the bases loaded and we had the right guys up there, I think it was a different ball game," Orioles interim manager Juan Samuel said.

Bard pitched a scoreless eighth before Baltimore, playing its second game under Samuel, scored twice in the ninth inning on a Scott Moore two-run double versus Joe Nelson to snap a 19-inning scoreless streak.

The punchless Orioles, who managed only six hits, went 1-for-9 with runners in scoring position and stranded nine, have been outscored 19-2 under Samuel.

"We're just trying to stay positive," Samuel said, "and the clubhouse is very positive right now."

Lester got himself out of a jam in the fifth when Lugo advanced Jones and Atkins to second and third base, respectively, on a sacrifice bunt for the inning's first out. But he induced Cesar Izturis to pop out to third and Patterson to ground out.

Pitch for pitch

Lester outpitched Guthrie (3-6) in a no-decision at Boston's Fenway Park on April 23. But this time, the Orioles hurler went pitch-for-pitch with the southpaw early on. He, too, was solid through six innings, retiring 15 Red Sox in a row before Dustin Pedroia singled with two out in the sixth.

Guthrie has lasted at least six innings in seven consecutive starts and allowed three earned runs or fewer five times but he's 3-3 over that span.

Youkilis deposited a first-pitch fastball over the fence to open the seventh inning for his 12th home run of the season and 17th career long ball versus Baltimore to give Boston a 1-0 lead.

"I'm trying to get ahead, trying to throw a good two-seamer down," Guthrie said. "The last time I checked, he was a two-time all-star, and he's paid over $9 million to hit a home run. He is as good as anybody. It just happened."

Youkilis said, "I just hit a fastball. He pitched well; we're very fortunate to get out with a win by grinding out at-bats."

With one out in the eighth, former Blue Jay Marco Scutaro plated Josh Reddick, who tripled to centre to begin the inning.

With files from The Associated Press