The Post’s Adam Kilgore discusses how much he expects the offseason acquisitions of starting pitcher Doug Fister and outfielder Nate McLouth to impact the Nationals in 2014. (Post Sports Live/The Washington Post)

In early September 2002, home in Indiana and done for the season, Jamey Carroll pondered his future in baseball. At 28, he had finished his seventh year in the minors. It was his best yet, but the Montreal Expos, handcuffed by an uncomfortable ownership structure, declined to call him up to the major leagues. Managers loved him, and he loved the game, but where was it taking him? Carroll went home and wondered.

“If I wasn’t getting called up then,” Carroll said, “then at that point in time, I was looking to see what was next in life.”

Twelve years later, Carroll is vying for the final spot on the Washington Nationals’ roster, hoping for one final year, to play at age 40 for the franchise he started with. A remarkable set of circumstances led to Carroll’s call-up, and that call-up led a remarkable career. He escaped the minors at 28 only because an infielder broke his hand and he could get to Wrigley Field quickly. He never went back.

In his second big league game, Carroll was the oldest position player in the lineup. He has played 12 big league seasons, swatted 1,000 hits, played in a World Series and earned more than $18 million.

In 2002, 113 players appeared who were 28 years old for the majority of the season. Three of them have been on a major league roster continuously since, including spending this spring at a big league camp. One is Ichiro Suzuki, perhaps the greatest international player in baseball history. Another is Derek Jeter, perhaps the most venerated player of his generation. The third is Carroll.

In the baseball public’s consciousness and in record books, Suzuki and Jeter dwarf Carroll. On out-of-the-way diamonds and cramped minor league bus rides, Carroll takes precedence, a model for coaches who need to convince a player his chance could come.

“Everybody uses him,” said Tim Leiper, Carroll’s last minor league manager. “He’s the guy. He’s the story.”

In the eyes of the Expos, Carroll entered the 2002 season as little more than a name. They had been taken over by Major League Baseball after the previous owner bought the Marlins. The revamped front office could safely ignore the former 14th-round pick who had hit .240 the previous year in Class AAA Ottawa.

Carroll started the season on the “phantom DL” at Class AA, Leiper said. But teammates and the few staffers left behind believed in Carroll.

“Joe Vitiello and I were just hammering Leiper all the time,” said Nationals bench coach Randy Knorr, Carroll’s teammate in Ottawa in 2002. “We kept telling Leip, ‘If you want to win, you got to play this guy.’ ”

“He’s so good defensively,” said Adam Wogan, then the Expos’ farm director and one of the few holdovers. “He can go anywhere. He is so sound fundamentally. I’ve never spoken to a guy that managed him that didn’t say he absolutely had to have the guy on his team.”

The lack of organization may have actually given Carroll his chance. With more structure above him, Leiper may have been forced to play a prospect. But with a patchwork front office, Leiper could play who he wanted, and he wanted to play Carroll.

“We can do this, but you’re going to have to play good,” Leiper told Carroll. “Or they’re going to figure out that I’m playing you too much.”

Carroll took over an everyday job, bouncing among shortstop, second and third. He batted .284, made seven errors all year and became Ottawa’s rock. With another team, he may have earned his first call-up. MLB disallowed the cash-strapped Expos from making more than two or three, though, and they sent him home.

On Sept. 9, Expos utility man Jose Macias suffered a broken hand at Wrigley Field. Already short on players, the Expos needed a versatile infielder immediately. Wogan believed Carroll could compete. Maybe more important, because Carroll lived in Indiana he could arrive in the clubhouse sooner than anyone else.

“I was the closest and could get there the fastest,” Carroll said. “From my understanding, that’s why I got the call.”

“I think the legend might have grown over the years,” said Wogan, now a scout for the Mets. “The question was asked, ‘Who’s nearby? Can he get here tonight?’ But I think he was also the most deserving guy.”

In his first game, having not played in two weeks, Carroll smacked two hits. In his second, he drilled two more singles and a double. Manager Frank Robinson kept putting him in the lineup.

“It seems like every manager he’s ever had said, ‘I need this guy on my team,’ “ said Leiper, now Toronto’s first base coach. “So many things had to happen right for him to do it. No matter how many times he got kicked, he continued to work hard. So many guys would have quit. If at any point he takes a day off, it just doesn’t happen for him.”

“I’ve always felt like I was that 25th guy trying to make the team,” Carroll said. “And that’s how I’ve always treated it. It’s just kind of how it’s always been for me. At the same time, I just kept that mind-set to keep me working hard.”

Carroll, who split his time last season playing for the Twins and Royals, already has made an impact in the Nationals’ clubhouse. The Nationals placed second baseman Anthony Rendon’s spring training locker next to Carroll’s. Carroll invariably arrives before Rendon — before any other player most days — and so Rendon begins each day by saying, “Hi, Jamey.” Then he picks his brain about anything — how to bunt, how to play second base, how to last.

“I think that might be why they put me next to him, just so I could learn,” Rendon said. “He’s been a great mentor for me.”

Nationals center fielder Denard Span played with Carroll in Minnesota and quickly came to appreciate him. Ninety minutes before first pitch, while the rest of the clubhouse watched TV or ate a snack, Carroll would be dressed head-to-toe in full uniform, spikes on and jersey tucked in.

“He inspires me, to be honest with you,” Span said. “Knowing how old he is and watching the way he plays the game, he never takes a play off, never takes anything for granted. I’m 10 years younger than him. Whenever I’m sore or aching, I look at him, and he kind of gets me going. Every team needs a guy like that.”

Will Carroll be the Nationals’ guy like that? The team remains open-minded about its final available bench spot. It almost certainly will come down to either first baseman-outfielder Tyler Moore or Carroll. Moore provides more power and an additional first baseman. Carroll brings dependability, exquisite defense, versatility and a steady voice in the room.

Three years ago, Carroll made it a goal to play in the majors at 40. He says he has not yet considered what he’ll do if the Nationals choose not to keep him. Whenever the end comes, he will understand the unlikely, incredible nature of his time in baseball.

“From the time getting called up and being 28, I’ve kind of had that appreciation,” Carroll said. “I didn’t think it was going to happen. I’ve never lost sight of that.”

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