The last time the A's and Angels met, on June 11, Oakland won, 7-1, and left Anaheim with a 3 1/2-game lead over Los Angeles in the American League West.
The A's were riding high for much of the season, but things have changed for them since that game. Oakland has lost eight of its last 10 games. In that span, Los Angeles has been hot, and the A's have gone from first place in the division to second.
Following their own loss and two Angels wins in the last two days, the A's have fallen two games behind in the standings.
"We've just gone through a tough stretch here, and really, the first one of the year," said A's manager Bob Melvin. "I never thought it looked like we were running away with it. I don't buy into that at all, these percentages you see up there to win the division and all that. It can be swung very quickly in three games. They're one of the best teams in baseball, and we know we're going to have some seriously emotional games against them."
The rivals will clash in a three-game series beginning on Friday at O.co Coliseum, with each remaining meeting between the clubs crucial to how the postseason picture will take shape.
But for Angels outfielder Kole Calhoun, the standings are not the only things that have changed.
"I think we're kind of a different team now than what we were then," Calhoun said. "It's going to be huge, man. It's going to be a dogfight. Two good teams going at it. They have a good pitching staff over there. They play good baseball, find a way to win games all the time. It's going to be fun. It's going to definitely be a battle."
As the A's have gone recently, so has their starter for the opener, right-hander Sonny Gray. After going 6-0 with a 2.11 ERA in seven starts prior to August, he is 0-4 with a 4.94 ERA in four starts this month.
Despite his recent struggles, however, he has an excellent track record against AL West opponents this season. In nine starts against division foes, he is 8-1 with a 2.00 ERA. He has also had success against the Halos, going 1-0 with a 2.45 ERA in three appearances (two starts) against them.
The Angels will counter with left-hander Hector Santiago, who has been pitching very well as of late. Over his last seven outings (five starts and two relief appearances in extra innings), he has a 1.39 ERA. He has also been fantastic in two starts against the A's this season, yielding one earned run in 13 innings against them.
Santiago is putting less pressure on himself now after beginning the season 0-6 with a 5.19 ERA.
"Especially with me [starting] one day and going to the bullpen, and going back and forth, like, 'This is my last start.' Whatever it is, five, six, seven innings, I just try to take that game as the last game of the year," Santiago said. "I just worry about today, and that's all that matters."
Angels: Calhoun continues to provide spark
Calhoun has been crucial to the Angels' success this season and has been providing a spark both offensively and defensively.
Over his previous 12 games, he was batting .391, with six doubles, two homers and 11 RBIs. He also led the Majors with a .514 slugging percentage as a leadoff hitter.
In Tuesday night's win over the Red Sox, Calhoun made a spectacular leaping grab at the wall in right field to rob Brock Holt of a three-run homer.
"I just kind of took a peek [at the wall]," said the 5-foot-10 Calhoun. "The ball was up there for a while, so I had time to get back. I knew I was close. I actually didn't think I was going to hit the wall. I thought I was going to come in kind of short, but I came down right on it and made the catch."
A's: Rotation shuffled for Angels series
The A's will skip Jason Hammel's next scheduled start, which would have come on Friday. With off-days on Monday and Thursday this week, Melvin decided to put the struggling Hammel -- 1-5 with a 6.75 ERA since being acquired in a trade with the Cubs -- in the bullpen on days when he isn't throwing on the side.
Hammel is expected to make his next start during the next series, in Houston.
"With these off-days, we've manipulated a little bit here," Melvin said. "But we still know that [Hammel is] very important to us, and we have to get him going."
• The A's have won six of nine games against the Angels in 2014. Including Friday's series opener in Oakland, the two teams will meet 10 more times this season.
• Mike Trout is 10-for-26 with five doubles, two homers and seven RBIs in his last six games against Oakland.
Manny Randhawa is an associate reporter for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.