WASHINGTON (AP) -- Justin Upton homered twice and had three RBIs, Matt Kemp added a two-run double and the San Diego Padres held on to beat the Washington Nationals 6-5 on Wednesday night.

Tyson Ross (9-9) allowed four runs in 6 1-3 innings for the Padres, who evened the three-game series and will try for their fifth straight series victory in Thursday's finale.

Denard Span doubled twice for Washington in his second game back from the disabled list following back spasms, but Gio Gonzalez (9-7) failed to pitch more than five innings for a sixth time in seven starts.

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Ryan Zimmerman drove in two runs on productive outs for the Nationals, who trailed 5-0 midway through the fourth before closing to within a run after a three-run seventh.

Craig Kimbrel pitched the ninth for his 36th save.

Ross struck out nine, including out seven of the first 12 batters he faced, while allowing six hits and two walks.

Upton's 21st and 22nd home runs of the season marked the Padres' 10th multi-home run game of the year and second in as many nights after Jedd Gyorko connected twice in Monday's loss.

Upton's first, a lined shot into the Padres' bullpen, brought in the final two runs of a four-run third. His second, a towering, opposite-field drive over the out-of-town scoreboard, made it 6-2 in the seventh.

In the bottom of the inning, Ross plunked pinch-hitter Clint Robinson before Span chased the hurler with his second double. Shawn Kelley then walked two batters to force in a run, and Bryce Harper's single to right-center off Marc Rzepczynski cut it to 6-5.

Yunel Escobar grounded into a 5-4-3 double play to end the inning.

Gonzalez allowed five runs -- four earned -- on seven hits and two walks in 4 2-3 innings. He has a 10.22 ERA over his last three starts.

TRAINER'S ROOM:

Padres: OF Wil Myers (left wrist tendinitis) hit in the batting cage Wednesday and could take live batting practice soon, said manager Pat Murphy. ... RHP Bud Norris (both obliques) was given the day off again Wednesday. Murphy doesn't think the injury "is anything long term."

Nationals: OF Reed Johnson strained an oblique muscle while rehabbing from a calf injury that has kept him out most of the season. "Strange happenings," manager Matt Williams said. "He got hit in the ribs, and then sneezed and pulled in an oblique in the same area." ... INF Dan Uggla (back spasm) is unlikely to return from the disabled list until rosters expand "unless there's a need," Williams said.

UP NEXT:

Padres RHP Andrew Cashner (5-12, 4.03) looks for his first consecutive wins of the season against Nationals RHP Joe Ross (4-5, 3.56), Tyson Ross' younger brother.