The Oakland Athletics squandered a big opportunity to take control of the American League West over the weekend thanks to an offense that suddenly struggles to score runs. The Athletics hope to have Adam Dunn available when they host the Seattle Mariners for the opener of a three-game series on Monday. Oakland totaled four runs in dropping four straight to the Los Angeles Angels, falling five games back in the division in the process.The Mariners are a half-game behind the Detroit Tigers in the race for the second wild-card spot, 4 1/2 games behind the wild-card leading Athletics. Oakland swung a trade on Sunday for the veteran Dunn, who is expected to serve as designated hitter against right-handed pitching and hopefully add some pop to the middle of the lineup that has been missing since Yoenis Cespedes was traded to Boston. Seattle is not blessed with the most potent offense in the world either, but got a home run and four RBIs from Dustin Ackley in snapping a three-game slide on Sunday.TV: 4:05 p.m. ET, ROOT (Seattle), CSN California (Oakland)PITCHING MATCHUP: Mariners RH Chris Young (12-6, 3.17 ERA) vs. Athletics RH Jason Hammel (9-10, 3.72)Young had his start pushed back and will be working on eight days rest after getting lit up in his last turn. The Princeton product was reached for three runs on seven hits and five walks in 3 2/3 innings at Boston on Aug. 23 but was held out of the decision when the Seattle offense picked him up. Young's last loss came against Oakland on July 13, when he was reached for three runs on five hits in six innings.Hammel has been sharp in three of his last four starts and held Houston to one run on three hits in seven innings on Tuesday. The veteran, who turns 32 on Tuesday, was skipped in the rotation his previous time through after allowing five runs in three innings at Atlanta on Aug. 15. Hammel is just 1-5 with a 5.77 ERA in eight starts since joining the Athletics.WALK-OFFS1. Athletics CF Coco Crisp (neck strain) missed the last two games and could miss a few more days.2. Seattle CF Austin Jackson has hit safely in 11 straight games.3. Oakland SS Jed Lowrie (fractured right index finger) is expected to come off the DL and start on Monday.PREDICTION: Athletics 5, Mariners 3