DETROIT -- The Oakland Athletics lost their starting pitcher before their game began Monday. The bullpen and Matt Olson's big bat bailed them out.

Olson homered for the fourth consecutive game and six pitchers combined to hold the Detroit Tigers to three runs in the Athletics' 8-3 victory at Comerica Park.

Olson's two-run shot in the third inning was his 11th homer in September and 14th in the past 20 games.

"It's a little unfair expectations, but it's been pretty spectacular for the amount of time he's been here and what he's done," Oakland manager Bob Melvin said of Olson's daily homer routine. "It's the first time he really ever gotten an opportunity to play every day and you see the offensive numbers, but defensively he's spectacular at first, too."

The Athletics' scheduled starter, Jharel Cotton, sustained a right groin strain while warming up and was a late scratch.

"I throw a flat ground before I go to the mound and the second pitch, that's when I felt a slight pull in my groin area," Cotton said. "I tried to see if was nothing and it just kept grabbing."

Emergency starter Raul Alcantara held the Tigers scoreless for 3 2/3 innings. Liam Hendriks (4-2), who pitched 1 2/3 innings of scoreless relief, was credited with the win.

Alcantara had only made two relief appearances since his September call-up.

"He really did (save us), for a guy who hasn't thrown more than 30 pitches in the better part of a couple of months, to give us what he did," Melvin said.

Jed Lowrie drove in three runs during the first four innings. Marcus Semien had two hits and scored three runs, Chad Pinder supplied two run-scoring doubles, and Matt Joyce added three hits and scored a run for Oakland (67-83).

The A's have won nine of their past 12 games.

Ian Kinsler had two hits, including a solo homer, and drove in two runs for Detroit (62-88). Nicholas Castellanos was 3-for-4, extending his career-high hitting streak to 15 games.

Kinsler said Oakland's late pitching switch threw off the Tigers.

"It's always kind of funky when that happens," he said. "You're preparing for one guy all day. It's basically like a bullpen guy coming in."

Detroit starter Buck Farmer (4-4) gave up five runs (four earned) and six hits in 2 2/3 innings. Batterymate James McCann said Farmer was dealing with tightness in his trapezoid.

"He struggled to get the ball to the glove side," McCann said. "Even in the bullpen he was struggling with it and he was never able to make the adjustment. He did for a couple of hitters at the end of the first inning. But that's part of it. You have to battle through something like that, but he just wasn't himself tonight."

Lowrie's run-scoring double in the first brought home Semien, who led off with a single.

The A's scored four runs in the third. Lowrie once again knocked in Semien, this time with a sacrifice fly. Olson crushed his 22nd homer to right-center field to make it 4-0, and Pinder's RBI double completed the outburst.

Oakland tacked on two more runs in the fourth for a 7-0 lead. Lowrie drew a bases-loaded walk, and the other run scored on Khris Davis' double-play grounder.

Detroit scored two runs in the fifth on run-scoring doubles by JaCoby Jones and Kinsler.

NOTES: Detroit RHP Jeff Ferrell was struck in the head by Ryon Healy's line drive in the eighth inning. He was immediately removed from the game. Ferrell underwent a CT scan but was alert and responsive while undergoing concussion tests, according to manager Brad Ausmus. ... Tigers LHP Matt Boyd had no regrets about the 2-0 changeup he threw to the Chicago White Sox's Tim Anderson on Sunday. Boyd was one out from a no-hitter when Anderson stroked an opposite-field double. "The pitch I wanted, the pitch I executed," he said Monday. "I slept easy on that note." ... The A's lead the majors in errors (118) and unearned runs (82). ... The first-inning double by A's 2B Jed Lowrie left him just one shy of Jason Giambi's season franchise record of 47 doubles. Giambi set the mark in 2001.