OAKLAND, Calif. — With a postseason berth within their sights, the Oakland Athletics are leaving nothing to chance.

Marcus Semien had three hits and a career-high five RBIs, Stephen Piscotty homered and drove in four runs and the Oakland Athletics hammered the Los Angeles Angels 21-3 on Thursday.

The Athletics reduced their magic number for clinching a playoff berth to five. Since June 15, Oakland is a major league-best 58-25.

Going into Thursday, Oakland trailed Houston by four games in the AL West, led Tampa Bay by 5 1/2 games for the second wild-card spot, and was 2 1/2 games behind the New York Yankees for the first wild card.

Catcher Francisco Arcia pitched the last two innings for the Angels, who were outscored 31-2 in the last two games of the series. He also homered in the ninth, becoming the first player in Major League history to catch, pitch and hit a home run in the same game, according to the Angels.

Red Sox 11, Yankees 6

NEW YORK — Mookie Betts and the Boston Red Sox won their third consecutive AL East championship Thursday night, clinching on enemy turf with an 11-6 victory over the rival New York Yankees.

Betts homered, doubled twice and drove in five runs, finishing with four hits as the Red Sox overcame Giancarlo Stanton’s go-ahead grand slam in the fourth inning. Jackie Bradley Jr. hit a tying home run in the seventh and Xander Bogaerts put Boston ahead with a sacrifice fly.

With the best record in baseball and a playoff berth already secured, Boston (104-49) closed out a once-tight division race with nine games to spare. J.D. Martinez and the Red Sox, alone in first place since July 2, will open the postseason at home on Oct. 5 against an opponent to be determined.

Never before had Boston finished in first place three years in a row. The club needs one victory to match the franchise record held by the 1912 World Series champions.

Braves 8, Phillies 3

ATLANTA — Luca Duda’s pinch-hit double drove in the go-ahead run in the seventh, and the Atlanta Braves took an important step toward winning the NL East by beating the Philadelphia Phillies 8-3 on Thursday night.

Atlanta leads the second-place Phillies by 6 ½ games following the opening game of the four-game series. The teams close the season with three games at Philadelphia, but the Phillies need to win at least three of four in Atlanta to retain hope of making the final series meaningful.

The Braves have a magic number of four over Philadelphia to clinch their first division title since 2013.

BLUE JAYS 9, RAYS 8

TORONTO — Justin Smoak homered with two outs in the ninth inning to lift Toronto past Tampa Bay, dealing a blow to the Rays’ wild-card playoff hopes.

Smoak hit his 25th homer of the season and third career walk-off blast. Sergio Romo (3-4) blew his eighth save in 30 opportunities. David Paulino (1-0) pitched an inning for the victory as Toronto won for the fourth time in its past five.

Trailing 8-2 to begin the ninth, the Blue Jays roared back to snap Tampa Bay’s five-game winning streak. Tellez hit an RBI double and Danny Jansen chased Jamie Schultz with a three-run homer. Romo came on and struck out Richard Urena, but pinch hitter Kendrys Morales singled and Lourdes Gurriel Jr. tied it with a two-run homer to left. Smoak followed with a first pitch drive to right.

TIGERS 11, ROYALS 8

DETROIT — Christin Stewart hit his first two big league homers and drove in six runs, leading Detroit past Kansas City.

Stewart, a September call-up playing in his 11th game, became the first Tigers rookie to drive in six runs in a game since Ryan Raburn had seven against the White Sox on July 25, 2007.

REDS 4, MARLINS 2

MIAMI — Cody Reed won for the first time as a starter in the majors, and Scooter Gennett homered and doubled to lead Cincinnati past Miami.

Reed (1-2) allowed five hits and struck out six in six shutout innings. The left-hander joined the starting rotation Aug. 30 and has thrown 11 consecutive scoreless innings.

Gennett’s two-run home run in the seventh gave Cincinnati a 4-0 lead.