OAKLAND, Calif. -- Sonny Gray still remembers the first time he faced the Pittsburgh Pirates as if it happened yesterday, not three seasons ago when he was a rookie.

The Oakland A's right-hander made his major league debut at PNC Park on July 10, 2013, and he pitched two scoreless innings out of the bullpen in a 5-0 loss to the Pirates. He struck out three and allowed one hit.

Gray will face Pittsburgh again on Friday, only this time he will start for the A's in the opener of a three-game interleague series at the Oakland Coliseum. He is bound to have flashbacks to his big league debut.

"I've got pretty cool memories, small memories I guess with the Pirates," Gray said Thursday before the Athletics' 12-6 loss to the San Francisco Giants. "That was a fun day."

In terms of wins and losses, this season hasn't been much fun for Gray, who is 3-6 with 5.03 ERA. He will take a five-game losing streak into his start Friday, and he hasn't had a victory since April 22 at Toronto.

Since being reinstated from the disabled list on June 5 after missing two weeks with a strained right trapezius, Gray has pitched well but has nothing to show for it. He is 0-1 with a 3.23 ERA in his past five starts.

"I still feel good ever since coming off the DL," said Gray, who went 33-20 with a 2.88 ERA in his first three seasons with the A's. "I still think it was the right choice to make. I didn't necessarily have to go on the DL, but that's the route we decided to go. Looking back at it, I think it was still the right call."

Gray and the A's will face a red-hot Pirates pitcher, Jeff Locke. In his past two starts, the left-hander is 2-0 with a 0.66 ERA, six strikeouts and zero walks. He outdueled Madison Bumgarner in a 1-0 victory against the Giants on June 20. Five days later, he pitched the Pirates to a 6-1 victory against the Los Angeles Dodgers and Kenta Maeda.

Before winning back-to-back games, Locke went 0-2 with an 18.69 ERA in losses to the Colorado Rockies and the New York Mets, who combined to hit .455 against him. Somehow, he was able to bounce back.

"The guy's pitching, and he's confident out there, even going through that rough patch, those back-to-back games you wouldn't really wish on anybody at this level," Pirates manager Clint Hurdle said after Locke's victory against the Dodgers. "He's handled it like a pro and just pitched through it."

Locke (7-5, 5.12 ERA) said a key to his turnaround was to stop being a perfectionist.

"Trying to make better pitches instead of perfect pitches," Locke said. "If it's a fastball away, just get it away."

Locke has faced the A's one time, on June 13, 2013, at PNC Park. He is 0-1 with a 2.57 ERA against Oakland.

The Pirates, who had an off day Thursday, have won four of their past six games. they snapped a six-game road losing streak Wednesday with an 8-1 victory against the Seattle Mariners.

The A's are 6-2 over their past eight games and have won back-to-back series, taking three of four from both the Los Angeles Angels and the Giants.

"We've definitely been playing well as of the last 10 games or so," Gray said.

The A's scored 34 runs in the four-game series against the Giants.