PHILADELPHIA -- The passing of the torch has been in the works for a while. It started on Aug. 5 when second-base prospect Isan Diaz was promoted from Triple-A New Orleans. To make room for the 23-year-old, veteran Starlin Castro agreed to slide over to third base.

A more formal rite of passage came on Sunday in poetic fashion. In the second inning, Castro belted a home run and two batters later, Díaz knocked a two-run homer in the Marlins’ 4-3 win over the Phillies at Citizens Bank Park.

• Box score

The Marlins salvaged the three-game series on Closing Day, finishing 57-105, and ended up 10-9 in the season series with the Phils, the lone National League East rival they had a winning record against.

“I'm not going to say this is the best season, but I think we have the guys here to compete,” Castro said. “Everybody is on the same page to help the team win. It's really fun to watch.”

Castro’s homer off Blake Parker was his 22nd, establishing a career high. In 2016 with the Yankees, Castro hit 21. He batted .302 with 16 homers and 52 RBIs following the All-Star break, after hitting .245 with six homers and 34 RBIs in the first half.

“That was cool for him to do that, also,” Miami manager Don Mattingly said. “We talked about him early, when he was struggling, [that] water reaches its level. Guys who do what they do, they end up there. That’s what we saw in the second half. His second half was huge. And playing every day. He played 162.”

Díaz’s homer was his fifth since being called up -- 31st of the season overall, when counting 26 at Triple-A. The potential that the left-handed-hitting second baseman brings is one reason the Marlins are upbeat about his future.

“A lot of learning,” Díaz said. “I had a blast. This is everything I expected it to be. Now I know what it is that I have to get better at. Next year, I'm going to come into Spring Training 100 percent better, for sure.”

The rookie had his struggles in 49 games, hitting .173, with a .259 on-base percentage.

“Isan has flashed what he can do,” Mattingly said. “I think he would probably admit this two months probably hasn't gone the way that he's thought or want them to. I think it's going to be valuable for him. It's going to put him in position that he's got some experience.”

Mattingly also noted that Díaz will come into Spring Training competing for a job.

“When he comes into spring, he's going to have to fight for a job,” Mattingly said. “Obviously, he's come here and hasn't knocked the door down and blew the house up and said, 'I'm your second baseman.' He's done some things that are really good, and he's had some areas that he's struggled.”

Sandy Alcantara (6-14), Miami's lone All-Star, worked six innings, allowing one run on eight hits in his franchise-rookie-record 32nd start. The 24-year-old finished the season at 197 1/3 innings and with an ERA of 3.88.

“I was thinking last night about throwing a complete game and to go home happy,” said Alcantara, who needed 8 2/3 innings to reach the 200 mark. “That didn't happen. A lot of pitches, but I never gave up.”

Tyler Kinley locked down the final two outs in the ninth inning for his first big league save, and he put himself in position to compete for a bullpen spot in 2020 after logging 49 1/3 innings with 46 strikeouts in 52 appearances.

The afternoon also featured a milestone for 35-year-old infielder Martín Prado, who notched his 100th MLB home run. One of the most respected players on the team, he became a Marlin in 2015, and he will be a free agent this offseason. Prado's career started with the Braves in '06. The homer was his second of the season, and first since April 24 at Cleveland.

Prado was replaced before the bottom of the ninth inning, with Jorge Alfaro taking over at first base and Marlins players embracing the veteran in what may be his final season in Miami.

“I didn't know,” Prado said. “They made that up in the middle of the game. I felt emotional.”

For the season finale, Mattingly handed over the reins to a veteran player. He has done that in each of his four seasons with Miami. Shortstop Miguel Rojas, who signed a two-year extension earlier this month, managed the club.

Prior to the game, the takeaway Rojas wanted to see the Marlins have was basic.

“Hopefully, everybody has paid attention to what the veterans on this club showed them, even without saying anything,” Rojas said. “You always pay attention to how Starlin prepares for games. How Martin goes about his business. How [Curtis] Granderson and [Neil] Walker lead by example. I hope every guy in this organization, and especially the younger guys getting their first opportunity of playing in the big leagues, pay attention to that stuff.”