Iwakuma struck out seven and didn't walk a batter as the Mariners won their second consecutive game against Oakland to begin the season. He gave up a leadoff homer by Yoenis Cespedes to the deepest part of center field in the second inning, then quickly regrouped and retired 15 of his final 16 hitters.
Kyle Seager doubled twice among his three hits, drove in a run, scored a pair and reached base five times. Kendrys Morales added an RBI single for Seattle, which is 2-0 for the eighth time in club history.
After King Felix and three relievers combined on the third opening day shutout in Mariners history Monday, Iwakuma did his part against the reigning AL West champions.
So did the hitters.
Morse, a former Mariners farmhand who returned to the franchise this season, had his sixth career two-homer game and first since Sept. 27 last year with Washington at Philadelphia.
Seattle tagged Jarrod Parker for four runs and five hits in five innings, working the count to raise his pitch total in a hurry. The right-hander, a 13-game winner last season as a rookie, walked three and struck out one. He led the A's pitching staff with 63 free passes last season.
Parker allowed consecutive singles to Michael Saunders and Seager to start the game but retired Morales on a popup and induced Morse's inning-ending double play. The pitcher also worked through the second unscathed before allowing back-to-back walks to Saunders and Seager in the third. Morales reached on a fielder's choice and Morse then sent a 2-2 pitch over the right-field wall. Josh Reddick slammed face-first into the fence trying to make a play.
Justin Smoak drew a bases-loaded walk as Seattle added a run in the seventh against Ryan Cook, who had a pair of four-pitch walks and a five-pitch free pass to go with a hit batter in a rough seventh. Oakland walked eight in all.
After almost daily lineup changes a year ago, A's manager Bob Melvin stuck with the same hitters in order for Game 2. The group held to three hits in a 2-0 loss to Hernandez a night earlier mustered just three more.
"My pen was shaking," Melvin joked.
Iwakuma got through a 1-2-3 first inning on 10 pitches and was unfazed after Cespedes connected. The pitcher, who posted a club rookie record 2.65 ERA in 16 starts last year, allowed two hits in six innings.
Raul Ibanez, whose late-game power during the playoffs last fall lifted the Yankees, earned a start in left field as he returns to the Mariners for the first time in five years since spending the 2004-08 seasons with Seattle.
A's reliever Pat Neshek received warm applause when he relieved in the sixth. Oakland's players and fans rallied around Neshek after his newborn son, Gehrig, died 23 hours after his birth just before the playoffs began last fall.
NOTES: Oakland RHP Bartolo Colon will make his first start Saturday at Houston since receiving a 50-game suspension for a positive testosterone test last Aug. 22. That means Parker, Tommy Milone and A.J. Griffin each will get two extra days of rest and No. 1 starter Brett Anderson one additional day with the team off on Monday. ... Injured A's SS Hiroyuki Nakajima, who began the season on the disabled list with a strained left hamstring, had a short workout on the field. ... By losing Monday night, Oakland's skid on opening day reached nine games - setting an AL record and matching the major league mark shared with the New York Giants (1893-1901). ... Seattle plays 14 straight games before its first off day. ... LHP Joe Saunders makes his season debut for Seattle on Wednesday night against Milone.