PHILADELPHIA -- Oakland A's second baseman Joey Wendle dreamed about the moment as a kid from Southeast Pennsylvania.

Growing up a Philadelphia Phillies fan and getting a chance to start not far from where he was raised, Wendle didn't disappoint the dozens of family and friends in the seats behind third base on Sunday afternoon.

Wendle's grand slam in the top of the sixth inning was the difference on Sunday afternoon as the A's topped the Phillies 6-3.

"I've done that about a hundred times in my backyard so it was certainly really fun today," Wendle said.

The 27-year-old, in his second September stint in the majors, stepped to the plate in the top of the sixth inning. Wendle cleared the bases on the first pitch, sending a grand slam shot deep into the seats in right field to give the A's a 6-3 lead they did not surrender.

The former West Chester University Golden Ram's second career home run was the counterpunch the A's needed when they got to the Phillies bullpen. After being stifled on Saturday evening by the Phillies relievers, Wendle's long drive off Edubray Ramos was a crack in the armor big enough to give the Athletics a series win in the final game of interleague play for both clubs.

"It's one thing to hit a grand slam to put your team ahead, it's another thing when you do it at home," A's manager Bob Melvin said. "This is a pretty close knit group of guys, especially the younger guys that we've brought up and Joey's been with them so they were really happy for them. Everybody knows that there's some sentiment involved when you get to play at home and everybody was pulling hard for him."

Returning to the majors after an 849-day absence, Phillies starter Henderson Alvarez initially looked like a regular in the rotation.

The righty was an All-Star in 2014, but shoulder injuries sidelined him for a prolonged period. He stifled the Athletics lineup early in the game, scattering just four hits over five innings of work, but the wheels fell off for Alvarez the second time through the lineup.

"I felt good," Alvarez said. "I was a little nervous, I have to admit, it was kind of like it was my first time in the big leagues but I know I've been here before."

Alvarez, after a clean three innings to start the game, ran into the A's power stroke that has been their key to success all season. Chad Pinder knocked the first pitch he saw from Alvarez in the top of the fourth out of the park, and first baseman Matt Olson followed with a solo shot of his own, his 21st of the season.

Pinder and Olson along with Chapman are only the second trio of A's rookies to each have double digit home runs.

"A lot of times when we win, we're hitting homers," Melvin said. "That's kind of our strength so certainly to get off to a good start with those two guys and then certainly Wendle's was not only terrific for us, but also for a local guy that gets to come home, gets a start, and ends up having a big game."

In a 2-2 game in the bottom of the fifth inning, Maikel Franco collected his third hit of the day in his return to the starting lineup, sending rookie J.P. Crawford home to give the Phillies a 3-2 lead.

The Phillies took an early lead thanks to a pair of unearned runs caused by third baseman Matt Chapman on a grounder in play by Phillies outfielder Aaron Altherr. Cesar Hernandez scored before Franco singled home Altherr later in the inning to put the Phillies on top 2-0.

Oakland starter Sean Manaea (11-10, 4.56 ERA) settled in after surrendering the unearned runs, giving up just one earned run over five innings of work and earning his 11th victory of the season.

NOTES: Athletics 1B Matt Olson has homered in each of Oakland's last seven series and is batting .297 (22-74) over that span. … IF Jed Lowrie is tied for second in Oakland history with 45 doubles this season. … Since the All-Star break, the Philadelphia Phillies are averaging 5.13 runs per game at home (154 runs in 30 games), which is third best among National League teams, trailing the Chicago Cubs and Colorado Rockies. … The Phillies and Athletics concluded just their sixth-ever series against each other. The A's lead 10-8 and the teams are 3-3 when playing at Citizens Bank Park.