But the ball bounced just high enough to glance off Daric Barton's glove to give the surging Mariners another win.
Smoak's two-out RBI single helped Seattle overcome a shaky start by ace Felix Hernandez to win for the 10th time in 12 games, 6-4 over the Oakland Athletics in a doubleheader opener on Wednesday.
"It's baseball, and that's what happens when you go on good streaks," Smoak said. "Stuff like that happens."
Corey Hart and Mike Zunino hit solo homers off Dan Straily, and the Mariners got the win in a game in which Hernandez failed to strike out a single batter for the first time in nearly six years.
Brandon Moss hit an RBI triple that capped a three-run seventh against Hernandez, but the A's could not hold a late lead and have lost six straight home games for the first time since September 2007.
"It's frustrating," A's manager Bob Melvin said. "We actually had good at-bats against (Hernandez) from the first inning on. Squared some balls up and hit some balls hard at people on top of it. Our approach was really good on him today. We just let it slip away in the later innings."
Michael Saunders led off the 10th with a single off Ryan Cook (0-1), stole second and went to third on a sacrifice bunt by Stefen Romero. After an intentional walk to Robinson Cano, Cook struck out Hart before leaving with a strained right forearm.
Dan Otero relieved and Smoak hit a high chopper off the glove of first baseman Daric Barton for the go-ahead single. Kyle Seager added an RBI single.
Yoervis Medina (2-1) stranded two runners in the ninth for the win, and Fernando Rodney pitched the 10th for his ninth save in 10 chances.
Oakland had concerns beyond the loss. Center fielder and leadoff hitter Coco Crisp left in the fourth with a strained neck. Crisp got hurt after crashing into the wall to make a leaping catch of Seager's two-out drive. Crisp was down on the ground for a few minutes, walked off under his own power and was replaced by pinch-hitter Craig Gentry in the bottom half. Crisp is day to day.
"The ability to hold onto that ball, hitting the (wall) out there, that's got to be tough to do," Straily said. "He's a tough guy and he's going to get through it."
This was just the second traditional doubleheader in Oakland in the past 16 years, with the other in 2011. The makeup game was necessary because a game was postponed April 4 when the field was unplayable after there was no tarp on it overnight. Erasmo Ramirez was to start the second game for Seattle against Drew Pomeranz, with the Mariners seeking their first four-game sweep in Oakland.
The A's took a 4-3 lead with three runs in the seventh against Hernandez, who was unbeaten in his prior 10 starts in Oakland. Gentry hit an RBI single and Josh Donaldson tied the game with a sacrifice fly before Moss' triple off the wall in left-center knocked out Hernandez.
Hernandez failed to strike out a batter for the first time Aug. 19, 2008, against the Chicago White Sox, ending a streak of 179 straight starts with at least one strikeout. He allowed four runs - three earned - and matched his career worst against Oakland by giving up 11 hits in 6 1-3 innings.
"No strikeouts, not a good breaking ball, not a good changeup," Hernandez said. "That's what happens when you don't have good stuff."
But the A's gave back the lead in the top of the eighth on an RBI single by Cano against Luke Gregerson.
NOTES: Oakland LHP Fernando Abad was charged with Seattle's run in the eighth, ending his scoreless streak of 14 1-3 innings to starts the season. ... Straily has allowed nine homers, tied with Milwaukee's Marco Estrada for most in the majors.