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8/22/2014 9:49 P.M. ET

Lower leg issues interrupt Blanks' rehab

OAKLAND -- Kyle Blanks, who began a rehab assignment two weeks ago for a strained left calf, has suffered setbacks and was scheduled for an MRI on Friday.

In addition to the calf issue, Blanks is experiencing soreness from the ankles down on both sides, according to A's manager Bob Melvin.

"It's actually all lower leg, heel, feet, both of them now," Melvin said Friday. "He's having some trouble."

Blanks was sent to Triple-A Sacramento on Aug. 9 once he could run the bases comfortably, and he is 9-for-21 (.429) with a home run in seven rehab games. He appeared to be nearing a return after playing Monday and Tuesday, but he has not seen any action since.

The right-handed first baseman has been on the disabled list since June 23. In 45 at-bats for the A's this season, he is batting .333 with two home runs.

Oakland acquired Blanks from the Padres on May 15 in exchange for outfielder Jake Goebbert and a player to be named.

Gentry returns from DL; Otero squeezed out

OAKLAND -- The A's were so desperate to get one of their better right-handed bats back in their sluggish lineup that they temporarily parted with one of their better right-handed bullpen arms to do so.

In activating outfielder Craig Gentry in time for a crucial three-game set with the visiting Angels, who are starting back-to-back lefties this weekend, the A's optioned Dan Otero to Triple-A Sacramento.

"We don't have too many guys here with options, and Otero's one of the most valuable guys we have here in the bullpen," said manager Bob Melvin. "It certainly is nothing that he's done to deserve going down, but with these two lefties coming up, we're trying to get Gentry back, so it was a hard one, but that's the decision that was made."

It was the product of another decision made this week to skip Jason Hammel in the rotation. Hammel, who does not have Minor League options remaining, will fill the void in the bullpen left by Otero, who was 7-1 with a 2.28 ERA in 71 innings spanning 56 relief appearances this year.

No other arm has proved as versatile as his.

"That's the balancing part of this," said Melvin. "What's there a bigger need for? We do have some starters that would suggest they can go deep into games. If we get deeper into games, we feel like we have three, four guys who can finish it out for us."

That didn't make his conversation with Otero any easier.

"He probably thought I was kidding at first," he said.

Gentry returned to the lineup Friday, batting second in his first start since July 27, when he suffered a broken right hand. He's batting .264 on the season, including .273 against left-handers -- and .407 against the Angels.

The A's hope this to be an invigorating series of sorts, following an ugly 2-8 stretch in which they hit .228 as a team, and they're not only getting a significant bat back in Gentry but game-changing speed.

"It definitely gets a pitcher's attention," said Melvin. "We've been lacking in our running a little bit recently. He's never afraid to run, creates a little bit more of a dynamic than we've had here since he's been out."

A's, firm examining new ballpark at current site

OAKLAND -- The A's announced on Friday that they've appointed an architectural consultant to explore design options for a baseball-only stadium at the existing Coliseum site.

The news comes less than two weeks after the Oakland Coliseum board unanimously ratified a 10-year contract with the A's, keeping them in Oakland through at least 2024.

The firm, 360 Architecture, which has worked with the A's since 2010, specializes in the planning and design of professional and collegiate sports facilities. The firm's recent notable projects include MetLife Stadium, home to both the Giants and Jets of the National Football League, and San Jose Earthquakes Stadium.

It's the A's hope that the firm can provide them a new state-of-the art venue at their current site, rather than elsewhere -- reflecting a significant component of the lease deal that requires A's owner Lew Wolff to enter "good faith" discussions about building a new ballpark in Oakland after several years of trying to move the team south.

Jane Lee is a reporter for MLB.com. Aaron Leibowitz is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.