OAKLAND -- Masahiro Tanaka had a Saturday afternoon that Yankees manager Joe Girardi called head-scratching.

Tanaka struck out 10 batters, just the second time he's had double-digit strikeouts this season, but the righty gave up three home runs in just four innings. He finished with five runs allowed on eight hits and one walk on 82 pitches as the Yankees dropped their fifth straight, a 5-2 loss to the A's.

"It's something we haven't seen before," Girardi said. "The last three years, he's been really good at that and at self-correcting. For whatever reason this year, he's having a hard time doing it. But you got to go back to work."

Tanaka is the first pitcher in Yankees history to strike out 10 batters in a game while pitching four innings or fewer. He's also the only pitcher in at least the last 100 years to strike out 10 and give up three or more home runs in a game while pitching four innings or fewer, which is something that irked him.

"It's very frustrating," Tanaka said. "You look at how we played, and we've used a lot of the relievers, so obviously I wanted to go deep into the game, eat up some innings. But I wasn't able to do that. I wasn't able to do a good job."

Tanaka gave up a home run on his first pitch of the game to Matt Joyce and then gave up two to Ryon Healy , who took him deep to left-center in the second and fourth. For Yankees catcher Austin Romine , the first inning was emblematic of Tanaka's odd day.

"I saw a guy ambush the first pitch in the game and hit a home run, but then [Tanaka] struck out the side," Romine said of Tanaka's three K's in a 12-pitch first inning. "It's the good and the bad. It's weird but you have to keep going with it."

Tanaka is now 0-6 with an 8.92 ERA in his last seven starts, and he has allowed 15 homers in his last 33 1/3 innings. He's given up 47 hits and walked 10 while striking out 44. Girardi was hoping his start in Anaheim Monday - where he went 6 2/3 innings and only allowed one earned run - was the start of something positive.

"I mean, you hope he can carry that over, the consistency he had there," Girardi said. "But it didn't start out great. ... It looked like he might be able to settle in, but he couldn't."

Despite his struggles, the Yankees feel like they went through a similar thing last year with Michael Pineda , who is throwing the ball well this season. Girardi remains confident that Tanaka will be able to find a way out of it.

"This is part of the game. You're always going to have some guys that are struggling a little bit," Girardi said. "I believe in him, and I've seen what he's done the previous three years. We'll just try to get him ready and get him going."