OAKLAND -- The surprising Oakland A's are surging toward the playoffs.
Meanwhile, the Boston Red Sox are closing out a disappointing season in freefall mode for the second consecutive year.
Two teams heading in different directions opened a series Friday night at the Coliseum, and the A's obliterated the Red Sox 20-2.
"Based on where we've been this season, the offense has been pretty good the last couple of months and certainly here during this stretch, so I don't know if I can ask for much more than 20 runs," A's manager Bob Melvin said.
Much of the damage came from three players who began their major league careers with the Red Sox. George Kottaras, Josh Reddick and Brandon Moss combined to go 9-for-15 with four homers, 13 RBI and nine runs.
Kottaras had career highs with two home runs and five RBI in Oakland's highest-scoring game in nearly 12 years.
"My priority is my defense and going out there for the pitchers," the catcher said. "I'm trying to call a game and do what I can defensively, and then the offense is bonus. But jelling with the guys and having a night like tonight definitely is a good feeling."
Reddick hit his first career grand slam to highlight Oakland's nine-run seventh inning.
"There's a little bit a sense of pride in there and satisfaction to show these guys what I'm truly made of," Reddick said of beating up on the Red Sox. "Anytime you (hit a grand slam) for the first time, it's a special thing, but once you add that it's against your former team, it's a little bit more special."
Moss went 4-for-4, hit a two-run homer and had a pair of run-scoring doubles. It was his first career four-hit game.
Josh Donaldson hit a two-run homer, and Jonny Gomes had two RBI singles during the Athletics' seventh straight win.
The A's have a one-game lead over the Baltimore Orioles for the first of two American League wild-card playoff positions.
The Red Sox, coming off a sweep at the hands of the Los Angeles Angels, have lost the first four games of their West Coast road trip.
"I thought they were trying," Red Sox manager Bobby Valentine said.
"Balls were just falling in and going over the fence. We had men on base and didn't cash in. Let's hope it gets better tomorrow."
Oakland's Brandon McCarthy pitched 6 1/3 innings and allowed eight hits and two runs to earn his first home win since June 19. McCarthy (8-5) has tossed at least six innings in 14 of his 17 starts this season.
"Being able to go a little bit deeper in the game is good, but I still would like to get deeper than 6 1/3," McCarthy said. "Especially on a night like that, I'd like to get through seven or eight (innings). I think that comes back to some quality pitches that could have been better, but overall it's pretty positive."
The 20 runs were a season high allowed by the Red Sox.
Boston starter Aaron Cook, a sinkerball pitcher, did not have the usual downward movement on his pitches. He was lit up for six runs on seven hits in 2 2/3 innings, recording only two groundouts.
"It (stinks) we got our (butts) kicked tonight," Cook said tersely. "How are we supposed to feel? We feel bad about it. We're going to try to come back tomorrow and do better. How would you feel if you got beat by 18 runs? Not too good. We're going to take a shower and move on."
The A's surged in front with a four-run rally in the second inning. Moss' double drove in Yoenis Cespedes for the first run. Moss scored on a Gomes single. Donaldson followed with a two-run homer to cap the inning.
The third inning included some deja vu from the second, as Moss hit an RBI double and was singled home by Gomes. The latter hit drove Cook from the game.
The second Boston reliever was Alfredo Aceves, the recently deposed closer. He gave up a two-run homer to Moss in the fifth, pushing Oakland's advantage to 8-1.
Oakland expanded its margin to 18-2 in the seventh.
Kottaras, who homered in the sixth inning, hit a two-run single. Cliff Pennington doubled in a run. Reddick hit his grand slam to right field, his 28th homer of the season.
After Adam Rosales doubled to right in the eighth inning, Kottaras made it an even 20 runs by hitting a line-drive home run to right field.
Red Sox catcher Jarrod Saltalamacchia homered in the fourth inning, his 23rd of the season.
NOTES: Red Sox second baseman Dustin Pedroia has an 11-game hitting streak. He has 995 career hits. ... Boston is a season-worst nine games under .500. ... Red Sox reliever Daniel Bard made his first appearance since June 3. He allowed one run in one inning. ... Oakland has tied its season high with seven consecutive victories. ... The Athletics have hit four or more home runs in a game on consecutive days. ... The A's recalled left-handed reliever Pedro Figueroa from Triple-A Sacramento for his fifth big-league stint of the year. Oakland demoted right-handed reliever Jim Miller to Class A Stockton, and he will return next week after the California League season ends. The A's didn't send Miller to Sacramento because the River Cats are headed for the Pacific Coast League playoffs.