BALTIMORE -- Once again, rookie lefty JP Sears performed well and continued to progress with another quality start, but for the second straight outing, it did not end in a victory for the Athletics.

Facing the Orioles for a third time on Friday night, Sears again offered his club an opportunity, as he gave up two runs on one walk to go with five strikeouts in six innings, while twirling only 81 pitches.

But he exited with the game tied and surging Baltimore scored three in the eighth inning, with the help of a critical error in judgment on defense that proved costly for the A’s in a 5-2 loss at Camden Yards.

"Fun night to be out there, great crowd, great to compete against a contending team,” Sears said. “Felt good about the performance. [Catcher Sean] Murphy caught a great game back there, good job from the defense tonight, just not enough to win."

One week ago, Sears surrendered three runs over six innings in a 3-2 loss to his former team, the Yankees.

With the series opener against the Orioles deadlocked at 2, indecision by A’s second baseman Jonah Bride on a ground ball ignited a game-altering, three-run O’s rally.

The inning began with an Anthony Santander walk against Oakland reliever Domingo Acevedo.

Ryan Mountcastle then sent a grounder to the rookie Bride, who hesitated looking to second base, then threw the ball too late to first. Mountcastle was safe easily with a base hit.

Following an intentional walk, pinch-hitter Adley Rutschman drew a bases-loaded walk to bring in the go-ahead run and Jorge Mateo followed with a two-run single.

"Obviously, a slow ground ball,” Bride said of the Mountcastle grounder. “[I] didn't realize he was getting down the line that quick, so should've just gotten the out.

"Definitely want to try to get that lead [runner] out, but probably wouldn't have had him there, so should have just picked it up [and] immediately went to first."

A’s manager Mark Kotsay said these lessons in games sting more for a 49-84 team trying to finish off a difficult season on a positive note.

"Yeah, they are tough,” Kotsay said. “That's part of our job as a coaching staff is to get in there and continue to teach, continue to make them aware of the mistakes and just keep working on it. They are growing pains. This one was a big one."

Whether Sears was pitching for the Yankees or the Athletics, he has been able to keep his team in the game when facing the Orioles.

Sears went 2-0 against the O’s earlier this season while with the Yankees, once as a reliever on April 16 here in Baltimore, and once as a starter on May 25 at Yankee Stadium. He allowed his first earned runs against Baltimore on Friday, but thanks to some solid defense and strategic pitching, he finished with another quality start.

The left-hander showed a great ability to trust his changeup and throw it for strikes, fanning Ryan McKenna on a called third strike in the fifth with three straight off-speed pitches. This after McKenna had singled off Sears’ fastball to lead off the game.

"He was telling me, ‘I feel good with it today,’” Murphy said. “So, we went down [in velocity] a little bit when we had to. Obviously, he felt good so he kept throwing it."

Said Kotsay: “His changeup was really impressive and it's a pitch that he's been working hard on, and knows he has to use it to keep hitters off that heater. It makes his fastball more explosive at the top of the zone and that really showed tonight."

The bottom of the Orioles’ order dropped in back-to-back doubles to begin the third inning, fueling a two-run rally that put the A’s in a 2-0 hole, thanks to an RBI bloop double from Robinson Chirinos and a run-scoring single from Mountcastle.

But Sears stayed with the game plan, and with solid defensive plays, kept the score down.

"The ball falls your way sometimes, sometimes it doesn't,” Sears said. “Definitely thought [it was] weak contact [by Chirinos], but just got to battle back and get back on [and] try to prevent that second run from scoring. [I] had a chance there with two outs and just made a bad pitch. Definitely some things to work on and get a little better at with runners on base."