SAN DIEGO -- Bryce Harper says he wasn't going for the double in his last at-bat at Petco Park Sunday afternoon.

"You try to have a good at-bat and put the ball in play and just get on base," said Harper, who needed a double in his final at-bat to complete the first cycle of his major league career.

Still ...

"Of course you try to get that double because it's a lot of fun,"

Harper continued. "But I'm just happy we got the win today and kept it going."

The Nationals completed a 5-2 trip to Arizona and San Diego Sunday with a 10-5 victory over the Padres that gave Washington three straight wins at the end of a four-game series at Petco Park.

Right fielder Harper went 3-for-4 -- and fell that double shy of the cycle -- while driving in four runs and scoring three Sunday to cap an 8-for-12 series that included a triple, two home runs, six walks and seven runs scored. Sunday's home run was Harper's National League-leading 14th of the season.

"Harper is locked in," said Padres manager Bud Black. "He is seeing the ball so well right now that he has no weaknesses. He's really swinging the bat well."

But it wasn't Harper's home run that turned the tide for the Nationals Sunday.

Danny Espinosa's three-run homer in the fifth, the second baseman's fifth of the season, erased a 2-0 Padres lead and put the Nationals ahead to stay.

Left fielder Tyler Moore also had a two-run double for the Nationals, who scored three runs in the fifth, four in the sixth and three in the seventh.

Right-handed starter Stephen Strasburg (3-4), a San Diego native and product of San Diego State, picked up the win for the Nationals, allowing three runs on five hits and a walk with seven strikeouts in five-plus innings.

"The command of the fastball was a little bit better today," said Strasburg, who entered the game with a 6.06 earned-run average. "This was a step in the right direction. It's just something I'm working through right now."

The lone bright note for the Padres was a pair of homers by Justin Upton, giving the left fielder 10 on the season. Upton's homers covered 387 and 368 feet. It was Upton's second multi-homer game of the season and the ninth of his career.

Right-handed Padres starter Ian Kennedy (2-3) allowed six runs on three hits and four walks in five-plus innings to get tagged with the Padres' fifth loss in the last seven games.

The Nationals turned the game around on one swing by Espinosa in the fifth after Kennedy nearly worked his way out of a hole. Kennedy hadn't allowed a hit and faced the minimum 12 Nationals hitters with six strikeouts through the first four innings.

But Harper opened the fifth with a triple off the wall in right, although he had to hold at third when Padres third baseman Cory Spangenberg made a diving stop of a single by Nationals first baseman Ryan Zimmerman over the third base bag.

With runners at first-and-third with no one out, Kennedy retired Moore and catcher Jose Lobaton on back-to-back infield pop flies -- bringing up Espinosa.

After taking strike one, Espinosa pulled Kennedy's next offering 383 feet into the right-field seats to erase the Padres' 2-0 lead.

"That was a big blow," said Kennedy, who has given up 11 runs on 11 hits and seven walks in 9 2/3 innings over his last two starts. "That game was frustrating. How it started and how it ended were two different games."

Kennedy opened the sixth by walking the only three hitters he faced and was replaced by left-hander Frank Garces, who entered the game to face Harper with no one out and the bases loaded.

After nearly throwing a breaking ball past Harper for a called third strike (plate umpire Phil Cuzzi called it a ball), Garces got Harper to hit a half-swing roller toward third that ground to a halt for a run-scoring infield single to make it 4-2.

Zimmerman greeted right-handed reliever Dale Thayer with a sacrifice fly to left and Moore shot a double inside the third-base bag to make it 7-2.

The Padres had used speed and power to forge a 2-0 lead.

Center fielder Abraham Almonte was struck out by Strasburg with one out in the first but reached on a wild. He stole second and was running to steal third when Kemp grounded an infield single behind second. Almonte never stopped running and scored. Upton made it 2-0 with his homer off Strasburg in the third.

NOTES: The Padres said OF Melvin Upton Jr. would treat his rehab assignment with Triple-A El Paso as spring training. Melvin Upton will get at least 50 at-bats with the Chihuahuas before he is activated from the disabled list. ... CF/1B Wil Myers took batting practice in the batting cage Sunday and is expected to return to action Tuesday. ... Nationals RF drew a walk in his first at-bat Sunday. He has drawn at least one walk in each of his last seven games and has walked in 27 of the Nationals' first 39 games. He leads the major leagues with 35 walk. ... LF Jayson Werth is scheduled to have an MRI on his left wrist Monday after the Nationals return to Washington, D.C. Werth hasn't played since being hit by a pitch Friday.