OAKLAND -- The Oakland A's had three-run homers from Khris Davis and Josh Phegley in a 14-5 victory against the Texas Rangers at the Oakland Coliseum on Monday night, but they left the game with their fingers crossed.

That's because rookie left-hander Sean Manaea exited after 4 1/3 innings with a strain of his left pronator muscle in his pitching forearm. The initial diagnosis is that Manaea's elbow ligaments are fine, but he'll have an MRI exam on Tuesday, and he doesn't know if he'll be able to make his next start.

"I have no idea," Manaea said. "We're just going to have to wait until the MRI tomorrow and go from there."

Manaea had a similar problem early in the season when was pitching for Triple-A Nashville. Then it flared up a little in his last start on June 7 at Milwaukee and again a day after a bullpen session in Cincinnati over the weekend.

"My first thought was it's pretty scary because I hear forearm stuff all the time and the TJ, that word," he said, referring to Tommy John surgery. " The doc took a look at my ligaments, said it was good from what he could tell. Just hoping the MRI says the same."

Manaea said he had trouble loosening up in the fourth inning against Texas and again in the fifth. That's when A's manager Bob Melvin noticed the velocity of Manaea's pitches drop and took him out.

Manaea gave up only two runs on four hits before exiting after giving up a home run to Shin-Soo Choo.

Davis hit his 15th home run of the season in the third inning, and Phegley had his first blast of the year in the fourth. Davis went 2-for-4, drove in five runs and scored three times. Marcus Semien and Jake Smolinski each had three hits, and every A's starter except Yonder Alonso had at least one hit.

"Just feeding off that momentum as far as good (at-bat) after good (at-bat) is what we want offensively to click," Davis said.

Rangers left-hander Cesar Ramos (1-3) gave up eight runs, six of them earned, on eight hits over 3 2/3 innings. He finished with five walks and one strikeout. He started in place of Yu Darvish, who went on the 15-day disabled list due to discomfort in his right shoulder.

"He was pressed into duty," Rangers manager Jeff Banister said of Ramos. "He got ground balls but they went for hits. Really, it's the five walks that were problematic. He kept falling behind, and it's a challenge to pitch when you fall behind like that."

Choo came off the disabled list and hit his first home run of the season, a solo shot in the fifth. Ryan Rua hit a two-run homer for the Rangers in the sixth, his fifth blast of the year, and Mitch Moreland hit his 10th homer in the ninth, a solo shot.

The A's lost the first seven games of their recent road trip, scoring a combined 15 runs during that skid. Then they finished the trip with a 6-1 victory at Cincinnati on Sunday before pounding out 17 hits and scoring 14 times Monday against Texas.

Ramos gave up singles to the first three A's he faced -- Coco Crisp, Semien and Danny Valencia -- to load the bases, but he allowed only one run in the inning. Davis brought Crisp home when he grounded into a force play.

The A's added four runs in the third to make it 5-0. Davis provided the biggest blow, sending Ramos' 2-0 fastball over the wall in left-center field for a three-run homer.

Davis, who has been battling an elbow injury, snapped a 10-game homerless streak.

"I hit it and I was like, 'Yeah, thank God, I can still hit it hard and through it,'" Davis said.

Ramos walked Billy Butler, gave up a single to Phegley and walked Smolinski, loading the bases. Alonso brought Butler home with a sacrifice fly.

Texas cut Oakland's lead to 5-1 in the top of the fourth, but the A's answered with five runs in the bottom of the inning. Semien singled with two outs, stole second and scored on Valencia's single. After Davis walked, Butler lined an RBI single off reliever Tom Wilhelmsen.

Phegley sent Wilhelmsen's 2-2 pitch over the right-center fence for a three-run homer, increasing Oakland's lead to 10-1.

NOTES: Rangers RHP Yu Darvish (right shoulder discomfort) was placed on the 15-day disabled list. He underwent MRIs of his right shoulder and his neck, but neither showed structural damage. ... The Rangers recalled LHP Alex Claudio from Triple-A Round Rock to take Darvish's place. Texas also activated RF Shin-Soo Choo (strained left hamstring) from the DL. Choo had been on the DL since May 23. ... Rangers OF Jared Hoying was sent to Round Rock. ... A's RHP Henderson Alvarez (right shoulder soreness) was scheduled to make a rehab start Monday for Class A Stockton. ... Rangers 3B Adrian Beltre (strained left hamstring) did not start for the fifth straight game. ... A's RF Josh Reddick (fractured left thumb) took 25 swings off a tee.