SAN FRANCISCO -- Two teams being cautious with injured players, getting acquainted with new ones and perhaps still shopping for upgrades, will hook up for a fourth time in four days on Sunday when the Washington Nationals take on the San Francisco Giants.

The Nationals have won two of the first three in the battle of National League division leaders, but the Giants are the ones coming off a 5-3 win Saturday.

On a day when the Nationals acquired a new closer, the Giants' new utility infielder, Eduardo Nunez, was one of the heroes in the win.

Nunez, picked up Thursday from Minnesota, collected two hits, including a two-run double that ignited a Giants comeback from an early 3-0 deficit.

It helped San Francisco avoid what would have been a fourth straight loss.

"That's the reason they brought me here," Nunez boasted. "To win games."

Nunez started at shortstop in place of Brandon Crawford, who suffered a bruised left hand in Friday's loss.

Giants manager Bruce Bochy said he hopes to have Crawford back in the lineup Sunday, which could mean a second position in two days for the versatile Nunez.

The Giants figure to have an opening in center field Sunday, with Denard Span likely to miss a second consecutive game because of a strained quad that occurred during a collision at first base in Friday's game.

Nunez has played 29 games in the outfield in his seven-year career.

The Nationals are hoping new closer Mark Melancon arrives in time for the series finale after having been acquired in a trade with the Pittsburgh Pirates shortly before the start of Saturday's game.

Washington dealt two left-handers -- major-leaguer Felipe Rivero and minor-leaguer Taylor Hearn -- in order to get the All-Star.

Even a midgame arrival by Melancon would be fine for the ninth-inning specialist, Nationals manager Dusty Baker assured.

"We're getting some reinforcements," the veteran skipper proudly declared.

Baker wasn't so confident about star second baseman Daniel Murphy after having sat him out of Saturday's game.

Murphy felt tightness in his left leg in the cold San Francisco weather during Thursday night's game, then tried to play through it on Friday.

He had to be pulled midway through the win, and was given the full game off Saturday.

"Still being precautionary," Baker said of Murphy.

He remains questionable for Sunday.

With trade winds swirling around both teams, Bochy and Baker are comforted in knowing they've got veteran starting pitchers going Sunday.

The Giants will go with 12-year veteran Matt Cain, who will be seeking his 100th victory in a San Francisco uniform.

Cain has a 5-5 record and 3.64 ERA in 15 career starts against the Nationals.

Washington will counter with nine-year veteran Gio Gonzalez, who spent his first four years across the bay from San Francisco with the Oakland Athletics.

Gonzalez sports a 3-3 record and 3.33 ERA in nine career starts against the Giants.

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