Oakland, CA (SportsNetwork.com) - Pablo Sandoval homered leading off the 11th inning to give the Boston Red Sox a dramatic 5-4 victory and send the Oakland Athletics to a sixth straight loss.

The opener of the three-game series went back-and-forth and was decided by which last-place team came through with the big hit.

Sandoval delivered when he lined an Angel Castro (0-1) 0-2 pitch over the wall in right, and Boston's bullpen, anchored by Matt Barnes, locked down the win.

The Red Sox used six relievers after Rick Porcello only lasted five innings. The last, Barnes (1-0), earned the win by stranding a runner in scoring position in the 10th and retiring the side in order in the 11th.

"Pablo had a big home run that put us ahead," said Barnes, who notched his first career win. "That first inning I was trying to keep it where it was and the second inning I was just trying to get those three outs and get the team a win."

Mookie Betts drove in two runs, and David Ortiz went 2-for-5 with an RBI for the Red Sox, who improved to 2-2 on their 10-game road trip.

The A's were coming off their own 10-game sojourn and are mired in their longest losing streak since dropping nine in a row from May 22-June 1, 2012. They fell to 1-11 in one-run games and 0-6 when playing extra innings.

"It's been the same story and it's tough to explain," A's manager Bob Melvin said of the close losses. "It's been a little surreal."

Billy Butler went 3-for-5 with a run scored and an RBI, and Stephen Vogt knocked in two runs in the setback.

Butler gave the A's the early lead with a two-out RBI single in the third, and both teams traded jabs in the fourth and fifth innings.

After Dustin Pedroia worked a walk, Ortiz laced Boston's first hit of the night into the left-field gap. Pedroia was running on the pitch and scored all the way from first.

Ike Davis doubled leading off the home half of the fourth and eventually scored on Marcus Semien's double-play ground ball.

Betts and Vogt traded run-scoring hits in the fifth, and after tying the game again in the seventh with an RBI single, Betts broke up a potential double- play ball off the bat of Pedroia to bring in the go-ahead run.

Boston's first lead did not last long, with Vogt's sacrifice fly in the bottom half pulling the A's even.

Game Notes

Monday's game was Boston's first of the season played outside the Eastern Time Zone ... Red Sox outfielder Shane Victorino went 0-for-4 after being activated from disabled list ... Edward Mujica retired the side in order in the eighth. The Red Sox traded the middle reliever to the A's last week for a player to be named later or cash considerations ... Oakland has committed at least one error in nine straight games ... A's starter Scott Kazmir was pulled after six innings having allowed just two runs on four hits and four walks ... Porcello was touched for three runs on nine hits ... The A's and Indians are the only teams in baseball without a win in their final at-bat ... The A's are 10 games under .500 (12-22) for the first time since finishing the 2011 season 14 under (74-88).