In the first game of the Philadelphia Phillies' 2023 MLB postseason run, in the bottom of the fourth inning with the Phillies up 1-0 on the Miami Marlins, Nick Castellanos belted a double. When he reached second base, he dusted himself off, pausing to look into the home dugout -- and proudly displayed a single batting-gloved finger on his right hand to his teammates cheering back at him.

Social media exploded, and even his own team's dugout was confused: Was the Phillies' right fielder flipping off his teammates from the middle of the diamond at Citizens Bank Park?

Castellanos later said that it was his ring finger he was waving in the air and that the gesture signified he wants a World Series ring to put on that finger, but for his teammates, this was just the latest case of Nick being Nick. This kind of thing is exactly what they've come to expect during his two years in Philadelphia. Ask anyone who shares a clubhouse with Castellanos what makes him tick and the inevitable smirk appears on that person's face. He's different, they say. But in a good way.

Shortstop Trea Turner put it simply: "He's one of one."

"I don't know if I've met anybody like him," Turner said recently. "He's different. And he can really, really hit. It's cool seeing him just do his thing. And regardless of what people think about him, he's just his own person. So I love him and respect him for that."

After a down year in 2022, Castellanos has burst onto the national scene during these playoffs. And it's not just his National League-leading five home runs this postseason for a team that will take on the Arizona Diamondbacks in an all-or-nothing Game 7 of the NL Championship Series on Tuesday night.

Beyond his play on the field and penchant for an attention-grabbing quote or celebration, his endearing relationship with his 10-year-old son, Liam, has also produced heartwarming social media moments that have helped make Castellanos a fan favorite in Philadelphia.

"Every day, being part of this team and getting to understand this city and being able to [spend time] with Liam, I'm loving my space here," Castellanos told ESPN.

Philadelphia has become a home, something for which the 31-year-old has been "searching" for a long time.

Castellanos was taken No. 44 overall in the 2010 draft by the Tigers, and he flourished at the plate as a doubles machine in spacious Comerica Park. But in his six years in Detroit, he made the postseason only once, in his rookie year, and for the latter part of his stay, he was one of few veterans on a perpetually rebuilding roster.

"I'm a dreamer by nature," Castellanos said. "When I was drafted as a Tiger, I thought of Al Kaline. I thought I was going to be like him. You don't always get Plan A."

Plan B turned out to be a trade to the Chicago Cubs at the 2019 trade deadline, just before he was scheduled to hit free agency the following offseason. Though he quickly became a fan favorite because of his scorching-hot performance at the plate -- he hit .321 with 1.002 OPS in 52 games -- Castellanos had trouble finding his place as a temporary answer in a clubhouse full of players who were part of Chicago's 2016 World Series roster.

"With the Cubs, I was a rental player," Castellanos said. "I was there for two months. I have all these visions and dreams and aspirations and theories on how things should go. But it was not my place to go in and do that because if I vocalized all that, I would have been viewed as a tyrant. That's also not in my personality either because any leader who inserts himself into that position, that's not a leader, that's a dictator. Over history, people don't f--- with dictators."

Though Chicago had made four straight postseasons, that year the team faltered late and Castellanos again missed out on playing in October. By that offseason, when Castellanos hit free agency, the Cubs were shedding salary instead of adding it, so Castellanos had an open mind in his search for a new home.

He ultimately signed a four-year, $64 million contract with the Cincinnati Reds that included opt-out clauses after each of the first two seasons. Coming on the heels of a career-best season in 2021, Castellanos elected to become a free agent for the second time in three years. Though he called his 2021 season "the most consistent, happiest I've been playing baseball" at the time, his performance had put his next contract into a dollar range the Reds were unlikely to spend, and Castellanos was again on the move.

The Phillies didn't actually emerge as a possible landing spot until late in the winter.

"I did not think that I was coming here during my free agent process at all," Castellanos said. "It wasn't [one of] the cities that I was interested in at the time, really wasn't on the radar. Then Bryce [Harper] reached out to me and said, 'What do you think? I want this. I want you to be here.'"

Harper's pitch worked, and over the span of three days in March, the Phillies signed Kyle Schwarber for $79 million and Castellanos for $100 million, remaking the team's offense (and leaving plenty of pundits wondering about its defense).

Asked if his fit in Philadelphia off the field was everything he had hoped for, Castellanos gave an emotional response that went far beyond the team's success on it.

"Yes," he said. "And it starts with the Middleton family. [Owner John Middleton] is a Phillies fan. He's a Philly guy. That's the foundation of everything. I truly do not believe that owning this team is a business for him. It's a passion. If that passion is not there, a lot of time, the things that are underneath it, does not work out. Because of that, he oversaw the hiring of [president of baseball operations] Dave Dombrowski. And I think Dave is tremendous at his job. And what makes him tremendous at his job is he's such a good people person. He believes in character above individuals.

"Every team is going to talk. I found that the more intelligent the words sound, the faker they are. The more fancy and educated the vocabulary -- you're getting to describe why winning is not now but it is in our imminent future -- they're trying to convince. I didn't have to be convinced here.

"The one thing that gave me comfort was having pillars in Bryce, J.T. [Realmuto], [Zack] Wheeler, Schwarber and Dave's track record. I didn't need to hear any intelligent vocabulary because if I can just look at what's there, I can understand."

Such a thought-out and detailed response to a question, any question, is something Castellanos' teammates have come to expect in their two years together.

"If Casty wasn't a ballplayer, he'd be a philosopher," catcher Garrett Stubbs said. "He'll always ask, 'Why?' No matter what. He's probably the most curious person in the entire world. It doesn't matter what the conversation is about. You know how little kids will always ask, 'But why?' He's always asking why, and it's hilarious."

Across the clubhouse, second baseman Bryson Stott admitted that learning to appreciate Castellanos' deeper thoughts to even the most routine conversations took some time.

"You could ask him the most simple question like, 'Why is it 7 a.m. in the morning?' and he gives you an answer you could probably write a story on," Stott said. "Sometimes you're like, 'Nick, I just want to know what time it is. I don't need to know about the sun and how everything is moving around.' Anytime you get in a conversation, you know you're going to get the most in-depth, full answer you could get."

Or you could get something off-the-cuff and shocking, in the vein of his ring-finger celebration. During an on-field interview after the Phillies' division series win over the Atlanta Braves, Castellanos was asked if his fit with the team was something he always needed. Without skipping a beat, he responded, "I mean, yeah, I f--- with Philly," on national television.

"I'm not sure where he's going with some of those interviews, like a lot of other people," Dombrowski said with a smile. "That's Nick. One thing you won't get is any false pretense. You'll either like it, or you won't. That's up to you."

There is no denying that Castellanos' straightforward approach could be jarring in a professional clubhouse. But the mistake, according to those who know him best, would be to judge Castellanos by only his quirky, say-anything style without getting to know him as a teammate.

Rookie center fielder Johan Rojas points to the help his right fielder has provided him all season, from the first day of spring training, to his call up to the big leagues in July, to the October stage. Throughout, Castellanos has been there to show the 23-year-old the ropes.

"He's been a mentor to me," Rojas said through the team interpreter. "He's been good about everything, really. He tells me what to expect in the game and sometimes when I don't have a good [at-bat], he comes to me to forget about it and focus on defense.

"All I can tell you is he's a great teammate. He's always looking to help me. I can't be more thankful to God for putting me on his team. He's been an incredible teammate."

Firmly in his comfort zone in his second year in Philadelphia, Castellanos has grown into a leadership role in the clubhouse and become a fan favorite. Much of what has endeared him to the home fan base is showing how he connects with his son through baseball. First, MLB released a Father's Day video tribute that showcased a softer, more personal side of Castellanos not many had seen before. Whether it's his son cheering him on after a clutch home run or a postgame trip across the parking lot to meet fans at Xfinity Live, their interactions this postseason have become part of the fabric at Citizens Bank Park. On the eve of NLCS Game 6, it was Liam who got the bigger ovation when both Castellanoses were shown on the Lincoln Financial Field scoreboard during the Miami Dolphins-Philadelphia Eagles game. Getting to share the journey with his son has added to the feeling of groundedness for the elder Castellanos.

"If what you mean by 'home' is I have like-minded individuals that are passionate about being great at their careers, yes, I have found a home," Castellanos said. "The city of Philadelphia, and the crazy cheering by the fans, is all complementary to that. Because if you don't have that, everything else is come and go.

"The more comfortable I feel with where I'm at, the more my raw emotions can come out and I'm not worrying, thinking or analyzing about s---. I'm just doing it because everything else is in its place."

Now, Castellanos and his Phillies teammates have a chance to finish what they fell just short of accomplishing last season -- bringing their city its first World Series title since 2008. But Castellanos refuses to let even that lofty goal be his only measure of success.

"There's two ways to go about it," he said. "You can look at the positive side and just appreciate the fact you got to be in it and not sound like a spoiled brat, just be thankful for the opportunity to play in the biggest baseball series in the world. Or you can be that much more frustrated and not be thankful about any of it and just want to finish it the right way, and none of the other stuff matters. Where's the balance?"

Many players would have given the expected canned response to such a question, but it's an answer that is quintessential Castellanos.

"Nick being Nick," pitcher Michael Lorenzen said. "He knows how to be himself better than anyone."