UPDATE, 5:50 p.m.: Manager Bruce Bruce Bochy just laid out his plans for life with Nori Aoki and Hunter Pence on the disabled list.

First off, there will be no set left fielder. Brandon Belt is playing there Wednesday night, but Bochy promised that we also will see just-recalled Travis Ishikawa and Justin Maxwell starting games (Maxwell likely in right when he plans, with Gregor Blanco moving to left).

Belt will continue to play some at first base, but Buster Posey might get more time there.

More for you Sports Giants' rotation logjam promises at least 1 constant

One beneficiary from all this could be Andrew Susac. Bochy said he would like to help fill the offensive void by having Susac catch more, which obviously means more Posey at first base.

Susac has not had a good offensive year, but part of that might be the infrequency with which he plays. He has only 78 plate appearances.

"I do think his more recent at-bats have been better, the quality of his at-bats," Bochy said. "His timing was off. When that happens, and you're not playing every day, it makes it more difficult. Hopefully with Andrew playing a little more, it's going to help him with the bat."

Angel Pagan has seemed lost at the plate in the past month. Bochy also sees better at-bats lately and said Pagan will get the lion's share of starts at leadoff, his old spot.

Bochy did not sugarcoat the Giants predicament with Aoki and Pence both out, and no set time for either to return.

"This is a big challenge. There's no getting around it," Bochy said. "We've had to go into this well before, challenged with injuries. Losing two key outfielders, that's why depth is important, too. We're going to have to have guys step it up. No question about it.

"You lose your leadoff hitter and a guy who hits in the heart of the order. Both are catalyst players. That's hard to overcome."

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So now to answer the question, why Ishikawa?

The short answer is, the Giants felt he was swinging the bat well at Triple-A and can play both first base and left field.

Some longer answers:

Outfielder Jarrett Parker showed in his brief callup that he was not ready to hit big-league pitching. Adam Duvall is crushing it in Triple-A again, but he is a first baseman who did not hit well when given a shot in the majors last year. Juan Perez has not had a good season at Sacramento.

I asked around about Mac Williamson, the Giants' best outfield prospect, who is hitting .296 with an .805 OPS in the pitching-rich Eastern League for Double-A Richmond, Va.

After all, the Giants benefited from bringing up Matt Duffy straight from Double-A last year and installing Joe Panik as the everyday second baseman as a rookie with Triple-A experience (after trying and discarding several more experienced options).

I was told the situation are different because Williamson, coming off Tommy John surgery, has played less than half a season over the past two years and needs at-bats. He's had only 284 plate appearances above A-ball. Duffy last year had 417 when he was called up, Panik 925.

What about trades?

Here's an analogy I've used before:

If you shop on eBay, you can bid for items and wait to see how the auction goes, but there's often a "buy it now" option that usually comes at a price that benefits the seller. You have to pay a little more to get the item immediately and ensure that nobody outbids you for it.

On June 24, teams seeking help via trade, especially those in dire straits like the Giants, have to pay the "buy it now" price in prospects, and right now, the Giants do not want to do that.

They would prefer to see how things shake out over the next few weeks. Perhaps the price for an outfielder they like will go up, but it also could fall depending on how many teams want him.

At the same time, the Giants also might need pitching, and might need to save their "inventory" of prospects to go that route.

In other words, no trades are imminent.

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Ishikawa was deadly honest.

When he had the choice last month of accepting an assignment to Sacramento or becoming a free agent, he stayed because he otherwise would have forfeited the roughly $800,000 left on his 2015 contract.

He could have negotiated a new deal with another club, but the money likely would have been less. Thus, staying with the Giants was "kind of a no-brainer."

Beyond the money, Ishikawa said, he and the Giants have a "comfortability" with one another because of their long association, which led to his pennant-winning home run against the Cardinals last season and a World Series championship.

Plus, he lives in the South Bay and liked the idea of playing close to home in Sacramento.

"There wasn't really a downside to not staying," Ishikawa said.

Well, there was one. Ishikawa had to swallow his pride and accept that the team did not see a spot for him after he completed his rehab assignment from a back injury.

However, the 31-year-old has been through the drill, having spent all or part of the past five seasons in the minors. In the days before the Giants designated him for assignment, Ishikawa did the roster math and saw it coming.

"Getting told you're not going to be on the team is always tough," he said. "Maybe because I had a sense it was happening softened the blow a little bit. I've gone through it six or seven times. It never gets easier."

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The Giants still would not provide a prognosis for Aoki other than saying he will be re-examined in about two weeks to see how well the fracture has healed

Bochy said he hopes Sergio Romo is available for a few hitters Wednesday after hyperextending his left knee the night before.

Finally, Pence is out of the splint he wore on his wrist for about a week, and hopes to be able to start swinging a bat again this weekend.

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UPDATE, 3:05 p.m: The Giants made the move official. They have purchased the contract of Travis Ishikawa and placed Nori Aoki on the disabled list with his leg fracture.

I shikawa is not playing tonight, however. Manager Bruce Bochy has penned a lineup with Angel Pagan leading off, Matt Duffy hitting third, Buster Posey at first base, Andrew Susac catching and Brandon Belt in left. (Right-hander Ian Kennedy starting for the Padres). Here it is:

1 . Pagan CF

2 . Panik 2B

3 . Duffy 3B

4 . Posey 1B

5 . Belt LF

6 . Crawford SS

7 . Susac C

8 . Blanco RF

9 . Vogelsong P

ORIGINAL POST: Before I left AT&T Park early Wednesday morning, I got a strong hint that the Giants are leaning toward purchasing the contract of first baseman Travis Ishikawa to replace Nori Aoki, who was diagnosed with fractured right leg.

You can read the entire story about Aoki here.

If the Giants follow through and promote Ishikawa, it would make sense on several levels.

He would provide a left-handed bat to replace Aoki's. Plus, manager Bruce Bochy would have the flexibility to move Brandon Belt to left field while having Ishikawa play first base against right-handed pitchers, while leaving Buster Posey behind the plate for the most part.

Ishikawa is hitting .269 with three homers in 33 games for Triple-A Sacramento.

The 2014 playoff hero was removed from the 40-man roster earlier this season when his rehab from a back injury ended and the big club had no spot for him, but he accepted an outright assignment to Triple-A to stay in the organization rather than become a free agent.

Henry Schulman is a San Francisco Chronicle staff writer. E-mail: hschulman@sfchronicle.com