Meanwhile, the Tigers were having all kinds of trouble with A's starter Tommy Milone, who lasted 6 2/3 innings, allowing four hits, walking two and striking out six.
Miguel Cabrera and Andrew Romine both doubled, and they were the only two Tigers in scoring position all day. Victor Martinez had two hits for Detroit.
Martinez has hit safely in 25 of his last 28 games, batting .366 with nine doubles, nine home runs and 22 RBIs.
"The offense is not the problem," Tigers' manager Brad Ausmus said. "Starting pitching is the issue. It's pretty clear cut. We're in a really long rut right now. It's still just seven games out of 162. I'm still fully confident this pitching staff is extremely good."
Anibal Sanchez, who pitches Wednesday night, has the Tigers' last two wins. Ausmus hopes he doesn't have to wait that long to kick-start his team on another winning streak.
"We wanted to turn this thing around three days ago, but it didn't happen," Ausmus said. "Hopefully Max [Scherzer] can take the ball [Tuesday] and help us right the ship. We really didn't do anything very well today."
The Tigers were hitless in five at-bats with runners in scoring position and are now batting .174 (15-for-86) in those situations over the past eight games. The Tigers have stranded 75 runners over that span and have been outscored, 67-31.
"Offensively, we were on it all day and just kept going after it," A's manager Bob Melvin said. "Getting add-on runs against a team like that is important, because you know they can come back at any particular time."
Smyly (2-3) lasted five innings, allowing six runs on eight hits. He walked two and struck out three for the Tigers, who lost for the seventh time in the last eight games since sweeping the Red Sox in Boston.
"I felt like I pitched OK," Smyly said. "I couldn't seem to keep it in the park. I'd get ahead in the count, and then leave a ball up, and home run."
The first four runs Smyly allowed were all solo home runs, two in the second and two in the third. He also gave up two runs in the fourth, though he did pitch out of a bases-loaded, no-out situation.
Smyly had given up four home runs in his previous nine starts.
The Tigers can usually depend on Smyly when he pitches on the road and during the day, but not against the A's.
He entered the game with a career 7-1 record and a 3.02 ERA in road contests, and had a 4-2 mark, with one save, and an ERA of 2.70 in daylight.
Smyly made three relief appearances against the A's before making his first start against them. He gave up five runs over 2 1/3 innings in those games.
The A's were 1-for-6 against Smyly with runners in scoring position. He's limited opponents to a .194 average in those situations this season.
"It wasn't a great outing for him," Ausmus said. "At least he got deep enough in the game where the bullpen wasn't completely torn apart."
Corey Knebel, who had allowed three runs in one inning in his first outing with the Tigers, pitched two scoreless innings. Phil Coke, who did not allow a run in his past two outings, coughed up Derek Norris' grand slam and was charged with two earned runs in an inning.
"I'm sure there are some tired arms down there," Ausmus said. "But they are part of a team and they have to pick up the starters right now."