OAKLAND, Calif. -- The rebuilding Oakland A's started six rookies, including right-hander Jharel Cotton, on Sunday against the Texas Rangers, a veteran team contending for an American League wild-card playoff spot.

Cotton pitched six strong innings, rookie first baseman Matt Olson hit a two-run homer, and rookie third baseman Matt Chapman added a solo shot and a defensive gem, lifting the A's to an 8-3 victory and a sweep of their three-game series.

"It definitely feels good," Chapman said of the sweep. "I think being able to sweep a team like Texas that's in the hunt, that has a lot of veteran guys and has been competing with teams around the league is a good confidence-booster for us, to know that we can compete with teams at a high level and we are capable of doing good things together.

"It motivates me personally to continue to get better and work with these guys. It just shows the kind of potential that we have as a team."

The Rangers (64-66) fell three games behind the Minnesota Twins for the second AL wild card.

"We obviously didn't swing the bats the way that we had been," Rangers manager Jeff Banister said of getting swept by an A's team that is in last place in the AL West. "I think any team gets momentum from their starters. This is a ballclub in Oakland that has given us challenges in the past in this ballpark.

"As we're getting closer, less games to play, we've got to find a way to play clean baseball, pitch it well and capitalize on our run-scoring opportunities."

Cotton (7-10) allowed two runs (one earned) on four hits and no walks. He matched a career high with nine strikeouts to win his second consecutive game after losing three straight.

Cotton opened the game by striking out Carlos Gomez and Shin-Soo Choo, both swinging, on changeups that followed mid-90s fastballs.

"That's the way I pitch right there," Cotton said. "Doing it at the beginning of the game like that was a confidence-booster to go the entire game like that."

Olson had a career-high three hits in four at-bats, and he hit his ninth home run and scored twice. Chapman went 3-for-4 with his 10th homer and scored three runs.

Choo hit his 16th home run for the Rangers, a solo shot. Adrian Beltre doubled twice and scored once.

Rangers right-hander A.J. Griffin (6-5), a former Athletic, allowed three runs on five hits, including two home runs, over 3 1/3 innings. He struck out three and walked three in his second start at the Coliseum against the A's.

"Just wasn't executing my elevated fastball," Griffin said. "I was trying to go up in the zone, and it'd be down by the knees of their wheelhouse."

Texas grabbed the initial lead for the third straight game, this time scoring an unearned run in the second inning. Beltre hit a leadoff double and scored from third with one out when A's second baseman Jed Lowrie dropped Mike Napoli's popup.

Oakland answered with three runs in the bottom of the inning. Matt Joyce led off with a single, and Olson launched a two-run shot into the right field seats with one out.

"Griffin's been kind of pitching at the top of the zone," Olson said. "Had a little ride on his fastball. So I just wanted to see something down, not chase anything up. He (threw) a couple fastballs. First one I took. The next one I saw it down and pulled the trigger."

Chapman followed with a solo shot over the high wall in left-center field, crushing a Griffin fastball.

The Rangers cut Oakland's lead to 3-2 in the fifth when Choo homered into the right field seats.

Oakland made it 4-2 in the sixth. Chapman hit a leadoff single, went to third on rookie catcher Bruce Maxwell's single and scored on Marcus Semien's forceout.

The Rangers cut Oakland's lead to 4-3 in the eighth. Carlos Gomez lined a leadoff single to center off reliever Chris Hatcher, went to second on a passed ball and scored from third with one out on Elvis Andrus' single to center.

Beltre followed with a double off the base of the left-center-field wall that left fielder Mark Canha appeared to misjudge, moving Andrus to third. Nomar Mazara was intentionally walked, loading the bases.

Reliever Blake Treinen took over, and Napoli lined out to third baseman Chapman, who raced to third to double off Andrus.

"That's huge," Melvin said. "It's either a double play or it's a ball in the corner and now we don't have the lead anymore. Quick reactions. He's ready for anything down there, whether it's on the ground or certainly a play like that."

The A's scored four runs in the bottom of the eighth, three of them unearned thanks to a throwing error by second baseman Rougned Odor. Olson, Chapman, Semien and Khris Davis each singled.

Treinen then threw a scoreless ninth inning to earn his seventh save.

After the game, the Rangers changed their travel plans because of the flooding and devastation in Houston in the wake of Tropical Storm Harvey. The Rangers, who are scheduled to begin a three-game road series Tuesday night against the Astros, had planned to fly to Houston. Instead, they will fly to Dallas and await a decision on the status of the series.

NOTES: A's rookie RHP Paul Blackburn (right hand contusion) will have a "follow-up" MRI exam and will likely be on the disabled list for longer than the team initially expected, Oakland manager Bob Melvin said. Blackburn was hit on the hand by a line drive off the bat of Orioles OF/INF Trey Mancini on Tuesday. He is still unable to grip a baseball. ... A's 2B Jed Lowrie left the game in the top of the sixth inning with a left shin contusion. He fouled a ball off his shin in the bottom of the fourth. "Just took him out precautionary," Melvin said. ... Rangers RHP Matt Bush (right knee sprain) has started to play catch and is "much improved," Texas manager Jeff Banister said. ... Rangers RHP Keone Kela (right shoulder soreness) has begun playing some "light catch," Banister said.