One of the casualties could be A.J. Burnett, who might make his final start in a Phillies uniform Wednesday night when he faces Pence and the Giants at Citizens Bank Park.
Pence helped San Francisco win the 2012 World Series after being acquired from Philadelphia, then had team highs of 27 homers and 99 RBIs last season to earn a five-year extension worth $90 million. Now in the role of table setter, Pence leads the majors with 73 runs while batting a team-high .305, and he was named the Giants' recipient of the Heart and Hustle Award on Tuesday.
"We're competing to win for each other, for my teammates," he told MLB's official website.
Since being traded, Pence has hit .389 with three homers in eight games against the Phillies. He's 6 for 13 with three RBIs and three runs halfway through this four-game set, posting a fourth consecutive multihit game and homering in Tuesday's 9-6 win in 14 innings.
Brandon Crawford had the tiebreaking three-run double and Tim Lincecum notched his first career save to cap the 5-hour, 46-minute marathon.
While San Francisco (56-44) has won five of six to reclaim the NL West lead, Philadelphia (43-57) is in the East basement and likely to shed salary before the July 31 trade deadline.
Burnett (6-9, 4.08 ERA) has a limited no-trade clause and couldn't veto a deal with Baltimore, according to MLB's site. He lives in Maryland in the offseason, and rumors have been floated that he'll be shipped to the Orioles.
The right-hander didn't boost his value Friday, when he was ripped for six runs and 10 hits in five innings of a 6-4 loss at Atlanta. He averaged more than seven innings in his final seven starts before the All-Star break while posting a 2.94 ERA.
"I feel I should make a pitch if I don't pitch in a week, whether we have a break or not," Burnett said. "... I have no excuses. I didn't get it done."
He might have a better chance to boost his stock Wednesday. Burnett has a 2.48 ERA in four matchups with NL West opponents this year even though he hasn't faced San Francisco, against which he's 6-3 with a 2.30 ERA - his best versus any opponent.
However, Pence, Buster Posey and Pablo Sandoval are a combined 8 for 18 against him.
Posey has batted .393 with 11 RBIs in his last six games after a four-hit night Wednesday, including the tying homer off Jonathan Papelbon in the ninth and a double that sparked a four-run 13th. Sandoval added two hits and is batting .409 in his last 10 games.
Unlike Burnett, Madison Bumgarner (11-7, 3.38) is coming off a strong showing after struggling before the break.
The left-hander beat Miami on Friday, yielding a run and four hits in six innings of a 9-1 victory. He had a 7.03 ERA in his previous four outings.
Bumgarner is 7-2 with a 1.94 ERA in 11 road starts but has never pitched at Citizens Bank Park. He's 1-2 with a 4.05 ERA in three career matchups with Philadelphia.
Papelbon, another Phillie possibly on the trading block, allowed his first homer of the season for his third blown save in 26 chances.
While the Giants are 6-0 on the road in extra-inning games, Philadelphia has lost eight of nine at home overall.
"It's just not going our way this year," Phillies veteran Ryan Howard said.