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6/14/2013 10:41 P.M. ET

Anderson to remain in walking boot four more weeks

OAKLAND -- The A's were hoping Brett Anderson's latest bone scans would show he'll be back pitching soon, not later.

But the results weren't favorable, so Anderson will remain in a walking boot for at least another four weeks, manager Bob Melvin said.

Anderson has already sported the boot for a month, but the stress fracture in his right foot has not fully healed. He'll be reevaluated in another four weeks.

That's when the All-Star break begins, meaning Anderson likely won't be pitching until at least the end of August, and that's if all goes well.

This news only adds to a frustrating series of events for the southpaw, who, still just 25, has been limited to 38 starts over the last three seasons because of four stints on the disabled list.

Originally placed on the disabled list May 1, Anderson had posted a 1-4 record and 6.21 ERA in six games, five of them starts, up to that point.

Cespedes returns; Crisp, Donaldson sit

OAKLAND -- A right hamstring strain forced Josh Donaldson to sit for just the second time all season on Friday, though his injury is not considered to be serious.

In fact, Oakland's third baseman is hoping to be back in the starting lineup for the middle contest of a three-game home set with the Mariners on Saturday, and manager Bob Melvin didn't rule it out.

Donaldson, joined on the bench by Coco Crisp, who is still dealing with right heel pain, entered the day 7-for-14 against Seattle starter Joe Saunders. Crisp has had plenty success too, going 9-for-30 off the lefty, but their absences were slightly mitigated by the return of Yoenis Cespedes, who had been relegated to the sidelines since Wednesday with a left hamstring strain.

"He's feeling much better," Melvin said of Cespedes, who started at designated hitter. "I saw him run out here earlier today. He was running without any issues. He might not be 100 percent, but hopefully he'll be guarded enough when he's running around the bases."

Melvin said Crisp felt better Friday morning despite playing four innings in Thursday's 18-inning affair with the Yankees. But "whether he's in the lineup tomorrow," he added, "I'm not sure."

Though there's just as much uncertainty surrounding Donaldson, the infielder is encouraged by the progress he's made in such little time.

Donaldson, who exited after 15 innings Thursday after feeling his hamstring "lock up a bit," says he is no longer experiencing "that knotting sensation" he endured for much of the night.

"It didn't feel like a cramp, but it could've been," he said. "I felt like if I was going to run hard, it wouldn't have been good. So I iced it, got treatment last night, and it's a lot better already."

"He felt a lot better than I thought he'd feel today," Melvin said, "so we'll hold out hope he can play tomorrow."

With Donaldson out of the mix, Adam Rosales started at third base Friday.

A's call up Otero, option Okajima to Minors

OAKLAND -- After using seven pitchers in Thursday's 18-inning marathon victory over the Yankees, the A's needed a fresh arm on Friday.

So they called on right-hander Dan Otero, who was dominating Triple-A competition, and decided to option Hideki Okajima, who appeared in just five games over the last month.

That meant Jesse Chavez remained in Oakland, even though he won't be available for a few days, after throwing 71 pitches in 5 2/3 shutout innings of relief while earning the win on Thursday.

A's general manager Billy Beane noted that a few days without Chavez is better than 10, which would have been the case had he been optioned. Plus, he said, he deserved to stay in the Majors.

"It was important to let him know he's a big leaguer," said Beane of Chavez, who has allowed just one run in 15 1/3 innings since his May 10 callup, after struggling in every other stint with the A's after they acquired his services last August.

"You have patience with guys like that, and some guys you don't if the track record isn't there," Beane said. "It's good to see Jesse contribute the way he did. You could just tell yesterday, when he was out there, his demeanor, he had a Major League demeanor. A lot of confidence."

"He was amazing," manager Bob Melvin added. "His last three or four outings for us have been the real Jesse Chavez. From the time we brought him up last year, he had a tough time of it. But the people in our front office and our scouts have been saying all along, this guy can pitch at the big league level and do well. He just needs to get on a little bit of a roll and gain some confidence, and we have definitely seen that the last several outings."

Otero's numbers speak to exactly why he was the one to get the call on Friday. The 28-year-old righty was 1-0 with a 0.99 ERA and .147 opponents' average at Sacramento, where he was perfect in 15 save opportunities. He struck out 22 and walked just one in 27 1/3 innings.

"You look at the numbers he's put up in Triple-A," Melvin said, "and they've been phenomenal, so probably well-deserved."

Originally claimed off waivers by the A's from the Yankees on March 29, Otero is with his third team in two years, having also played in the Giants organization. It was there where he made his Major League debut last year, posting a 5.84 ERA in 12 relief appearances spanning three stints.

To clear a spot on the 40-man roster for Otero, the A's transferred Brett Anderson to the 60-day disabled list.

Worth noting

• A's catcher Derek Norris and Yankees second baseman Robinson Cano exchanged a few words in the 13th inning of Friday's 18-inning contest. Norris believed Cano was stealing signs, and Cano was rather upset over these suspicions. On Friday, Melvin downplayed the minor flare-up.

"It was just boys being boys," Melvin said. "You get that a lot. Someone thinks you're tipping pitches, and you get emotional about it. It's not the first time it's happened, and it won't be the last. For me, it wasn't a big deal."

• According to Elias, the A's are just the second team in Major League history, next to the 1967 Yankees, to win two home games of 18 innings or more in one season. Overall, they're 7-1 in games of such length since moving to Oakland in 1968.

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