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5/10/2014 9:19 P.M. ET

Melvin unsure of when Crisp will return

OAKLAND -- Coco Crisp remains day to day with a sore neck. A's manager Bob Melvin said he'd like to see his center fielder go through a series of baseball activities before putting him back in the lineup.

Crisp underwent an MRI on Friday, which revealed no further damage.

"He feels a little better," Melvin said. "I'm not sure about his return until we get him back on the field and taking batting practice."

Crisp currently has a .260 batting average and a .354 on-base percentage. He has three home runs and 11 RBIs.

A's lefty O'Flaherty takes step toward return

OAKLAND -- Athletics left-hander Eric O'Flaherty was encouraged after throwing to hitters Saturday for the first time in nearly a year.

O'Flaherty, who signed with the A's in January and had Tommy John surgery on May 21, 2013, threw 20 pitches to Daric Barton ands Jake Elmore after tossing 15 pitches in the bullpen.

"It felt great," O'Flaherty said before the A's played the Nationals on Saturday night. "This is a big step forward. I'm very encouraged."

A's manager Bob Melvin said the team is looking at a mid-June return for the reliever. 

"Originally, we were looking at the All-Star break," Melvin said. "There is a lot to be excited about."

O'Flaherty would add yet another arm to an already-talented bullpen. In 2011 with Atlanta, he became the first relief pitcher to record an ERA under 1.00 with at least 70 appearances in a season.

O'Flaherty, who has been on a two-day-per-week throwing schedule, threw all fastballs Saturday, and will likely mix in some of his other pitches in another session before being sent on a rehab assignment.

"The ball came out of his hand real nice," Melvin said. "I'm sure he was excited about it."

A's Johnson showing closer form of late

OAKLAND -- Jim Johnson was signed to be the Athletics' closer this season, but a poor start forced Oakland to utilize a closer-by-committee format.

That may be changing. Johnson is 3-0 with a save and has not allowed an earned run over his last 10 outings, a span of 12 innings.

"We're not afraid to close with him, or with some other guys," A's manager Bob Melvin said. "Right now, there is no set closer, but he has put himself into position to be in there."

Johnson is one of three relievers who have saved games for the A's this season, joined by Luke Gregerson, who has three, and Sean Doolittle, who has one.

Johnson's recent streak dropped his ERA to 4.11, slightly better than Doolittle's 4.24.

The A's bullpen owns a 2.65 ERA, tops in the American League.

Doolittle's current streak of 29 innings without issuing a walk ranks fourth in Oakland history. He has also stranded his past 25 inherited runners, a streak that dates to June 22 of last year.

Worth noting

• Arnold Leon, who was brought up for Wednesday's doubleheader as the A's 26th man, was the first rookie to appear on Oakland's roster this season. Leon did not appear in either game and was sent back to Sacramento. That means Oakland is still the only team in the Major Leagues that has not used a rookie this season.

The streak of 36 consecutive games without using a rookie is the longest in Oakland since beginning the 1984 season without using a rookie for 73 straight games. Current pitching coach Curt Young was the rookie who ended that streak, on June 26, 1984.

Rick Eymer is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.