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4/27/2014 2:36 P.M. ET

Cespedes expected back at Texas

HOUSTON -- Yoenis Cespedes was missing from Oakland's lineup for a third straight game on Sunday, but the A's are hoping to have their left fielder back for a pivotal three-game set in Texas this week.

Cespedes, who suffered a mild left hamstring strain at Minute Maid Park on Thursday, wasn't even considered a viable option off the bench in Sunday's series finale in Houston.

"Initially I thought Texas was more realistic for him," said A's manager Bob Melvin, "and I'm probably still there with that."

Brandon Moss again got the start in left field with Cespedes out of the mix Sunday, batting in his usual cleanup spot. Alberto Callaspo hit in the fifth spot, where Cespedes has been hitting on most days this year.

In Cespedes' three seasons with the A's, the club is 179-103 with him in the starting lineup and 26-40 when he doesn't start.

Melvin still confident in 'pen

HOUSTON -- The A's entered the season with what was considered to be one of the game's best bullpens. Through the first 24 games, its American League-best 2.67 ERA suggests it's just that.

Except Oakland's relief corps has also already racked up six of the club's nine losses, along with six blown saves in 11 chances.

So, what gives?

"Any time your bullpen absorbs some losses, it means you are losing some close games," manager Bob Melvin said in advance of Sunday's game in Houston. "We're not used to that. Last couple years we've won most of them. We're off to a little bit of a slow start as far as that goes."

The A's are 4-4 in one-run games and 1-4 in two-run games. Last year, they were 30-20 in one-run games.

But the season is still young, and Melvin knows his relief crew remains "a very talented bullpen." Its quality of depth is perhaps unmatched.

"It won't continue this way, in my opinion," Melvin said. "You go through a slump, whether it's offensively, whether it's defensively, and it can happen in that fashion, too, with the bullpen."

This funk may be just that, but there is a major difference in the dynamic of this year's bullpen that has nothing to do with new names. The A's are playing with a closer-by-committee approach, which is good for matchup purposes, but not widely used since most relievers are most comfortable with set roles.

But Melvin noted Sunday that his relievers learn their roles for each game ahead of time.

"It's not like they don't know," he said. "We're pretty communicative on a day-to-day basis. It might not be like it is where you set your roles early in the season and you might not have another discussion because they know exactly what's going on. But we try to be communicative every day to try to combat that.

"If there are certain guys who aren't available on a certain day, we let the others know, OK, this is your inning today, and these are the guys we're looking to set up today, and this is how we're looking to get to the closer spot."

Worth noting

• Melvin said he's unlikely to make any changes to his rotation despite an off-day Thursday. With Sonny Gray, Scott Kazmir and Jesse Chavez scheduled to pitch in Texas, that means Dan Straily is likely to get the nod for Friday's three-game series opener in Boston. He'll be followed by Tommy Milone and Gray.

Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.