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7/9/2013 10:17 P.M. ET

Marcum to have surgery, season over

SAN FRANCISCO -- Mets right-hander Shaun Marcum has been diagnosed with thoracic outlet syndrome and will undergo season-ending surgery Monday in St. Louis, assistant general manager John Ricco said Tuesday.

Marcum experienced tingling and numbness in his right hand during his past two starts. He was examined Monday in St. Louis by Dr. Robert Thompson, who will perform the surgery.

"So the two courses of treatment would be conservative, which would be rehab, or surgery," Ricco said. "And Shaun has opted to have the surgery. And that is the recommendation of our doctors as well.

"It involves an artery that's blocking circulation. It's something that's impeding circulation, and they go in and do a procedure that frees up the blood flow."

Ricco said that "based on the diagnosis," Marcum will not be able to pitch again this season.

"What they've told us is he may be able to begin throwing in a couple of months. That would put him in early September," Ricco said. "I don't think there would be enough time for him to get back to the big leagues."

Marcum is 1-10 with a 5.29 ERA. In his last start on Saturday at Milwaukee, he allowed six runs (five earned) on 11 hits in five innings of a 7-6 loss to the Brewers.

The Mets recalled right-handed reliever Gonzalez Germen from Triple-A Las Vegas, and he was activated for Tuesday night's game against the San Francisco Giants, taking Marcum's roster spot.

Right-hander Carlos Torres will move out of the bullpen and take Marcum's spot in the rotation until Jon Niese recovers from a shoulder injury and returns from the disabled list, manager Terry Collins said.

Torres went 6-3 with a 3.89 ERA in 12 starts for Triple-A Las Vegas before being recalled June 15. In eight relief appearances with the Mets, he has allowed one run over 13 2/3 innings and has an ERA of 0.66. Torres said he has "no preference one way or the other" when it comes to starting or relieving.

"Everyone in the bullpen has been stepping up and doing a great job, and the starters have been keeping us right there in the game. We're all ready to go no matter what you ask us to do," Torres said.

Collins said there's a "possibility" Torres could start a game before the All-Star break if he decides to skip right-hander Matt Harvey's scheduled turn in the rotation Saturday. Harvey has been battling a blister on his right index finger. He's also on the National League's All-Star team and is considered to be a candidate to start the game Tuesday at Citi Field.

Although Collins said Harvey's finger looked "tremendous" Tuesday, he acknowledged it's still an issue in his decision on whether to skip Harvey's turn. Collins also said he will try to cut back on Harvey's workload.

"It's mostly about the finger, which has a little play about the All-Star Game, for sure," Collins said. "We're in discussions right now. [Pitching coach] Dan [Warthen] and I are trying to figure out how to start to cut this guy back a little bit. We'll have to decide what happens on Saturday. ... We'll start to limit it in various ways to make sure he's still strong and pitching well at the end of the season."

Aardsma enjoys pitching in former park

SAN FRANCISCO -- Mets right-handed reliever David Aardsma had a homecoming of sorts Monday night at AT&T Park against the San Francisco Giants.

For the first time since the Giants traded him on May 28, 2005, to the Chicago Cubs, Aardsma pitched at AT&T Park against his former team.

Aardsma pitched 1 2/3 scoreless innings during the Mets' 4-3, 16-inning win. In four career appearances against the Giants, he has yet to allow a run. He's held the Giants to two hits over 5 1/3 innings, striking out eight and walking one.

Pitching at AT&T Park was special but had nothing to do with payback, Aardsma said.

"It's great being back," said Aardsma, who was drafted by the Giants with the 22nd overall pick in 2003. "It's just as lively and great as it was back in 2004 when I was here. It's a pleasure.

"I have great memories. I have no bad feelings about it," he said Tuesday of the trade. "I loved my time here with the Giants. I think they're a great organization. Great city. I actually lived here a little bit even before I was a Giant. So I love this this city. I love the area."

Aardsma went 1-0 with a 6.75 ERA in 11 relief appearances in 2004. The next season, he was starting in the Minor Leagues when the Giants traded him and right-hander Jerome Williams to the Chicago Cubs for reliever LaTroy Hawkins, his current Mets teammate.

"I didn't expect it," Aardsma said. "I was in Double-A, pitching very well. They wanted me to become a starter. It was going very well. Then I got traded. It was a shock."

The fact that the Giants traded him to the Cubs, his "dream team," eased the blow. He grew up in Denver watching the Cubs on WGN.

Aardsma signed this season with the Mets on May 20 after being released by Miami. He's 1-0 with a 2.63 ERA in 14 appearances with the Mets and has stranded all eight inherited baserunners.

Worth noting

• The Mets made baseball history Monday night when they beat the Giants, 4-3, in 16 innings. According to the Elias Sports Bureau, the Mets became the first team in Major League history to play four games of 15 or more innings prior to the All-Star break. They also took a 4-3 loss at Miami in 15 innings on April 29, a 2-1 loss vs. Miami in 20 innings on June 8 and a 5-4 loss vs. Arizona in 15 innings last Thursday.

The Mets' latest extra-inning game came after they flew Sunday from Milwaukee to San Francisco.

"They're getting tired, very tired," Collins said of his players before Tuesday night's game against San Francisco.

• Right-hander Scott Atchison (sore right groin) pitched one inning Monday for the Rookie-level Gulf Coast Mets during a rehab assignment. He allowed two hits and one earned run and struck out two. He was placed on the 15-day disabled list June 19.

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