In baseball's sabermetric revolution, statisticians have become obsessed with determining a player's value in terms that are far less circumstantial than RBIs and far more telling of a player's ability to avoid making outs than batting average.
Perhaps the most advanced stat born of this revolution is Wins Above Replacement (WAR). WAR, which is not a uniformly agreed upon formula, seeks to measure the number of wins a player is worth above what could be expected by plugging a bench player or Triple-A callup into that player's slot in the lineup. An All-Star-caliber player logs about five WAR for a season, while an MVP usually logs upwards of eight.
In his four previous big league seasons, Pagan registered 829 plate appearances and never entered more than 88 games in a season. But with Mets center fielder Carlos Beltran starting 2010 on the disabled list after offseason knee surgery, Pagan was plugged into the starting lineup, just as he helped fill in for Beltran at the end of last season.
The Mets turned to a replacement player, but got something else entirely.
"He's driven in a lot of big runs. He's played extremely well. You're talking about a guy who, at the end of the first half, had a .315 average," Mets manager Jerry Manuel said. "You're also talking about a guy that steals bases, played a good outfield ... You've got to give Angel every opportunity now."
Now, Beltran is back for the second half and the Mets' outfield is suddenly crowded with the two center fielders as well as Jason Bay and Jeff Francoeur, who have started for their whole careers, manning the corner spots.
"We have four great outfielders," Pagan said, "and that's a good problem to have because you feel comfortable with whoever is playing."
But the problem isn't that the Mets have four equally capable outfielders.
The problem is that Pagan has played his way into a starting role.
Simply plugging Beltran back into center and sitting Pagan on the bench wasn't an option, based on Pagan's eye-opening first half.
According to Fangraphs.com, Pagan's .306 batting average, .827 OPS, seven home runs, 43 RBIs, 20 steals and stellar defense has equaled 3.2 WAR, which is good for 23rd in the Major Leagues.
By comparison, Bay has contributed 1.3 WAR and Francoeur actually comes in at negative 0.1, due in large part to his .296 on-base percentage.
The only Met that has been more "valuable" than Pagan thus far is David Wright, whose 4 WAR ties him for seventh in the Majors with Evan Longoria. The Rangers' Josh Hamilton and the Twins' Justin Morneau are tied at the top with 5 WAR.
Pagan, whose main preseason goal was to stay healthy this year, has new goals for the stretch run thanks to the amount of unexpected success he has enjoyed.
"I'm working even harder now," said Pagan, "making sure I do my routine every day, because the first half is the first half, but the most important half is the second one because this one defines whether your team is in the race or not."
To Manuel's credit, in an effort to best keep his team in the divisional race, he immediately identified Francoeur as the outfielder who would suffer the biggest loss in playing time and was straightforward with the wildly popular clubhouse leader and media favorite.
Though Beltran was absent during the team's solid first-half run, it was never a question of whether he would have a position to come back to.
"I hope [everyone understands], he's our best player," veteran infielder Alex Cora said of Beltran. "It's one of those situations, it's like pulling a trade. It's going to re-energize this lineup. It's going to be a better lineup with him. You put him in the middle of the lineup with what David is doing, it's going to make everybody better and help everybody out."
So far that hasn't been the case, as the Mets have dropped five of their first six games since Beltran rejoined the team after the All-Star break, a record due largely to the offense's ability to muster just 12 runs over that stretch.
That isn't an indictment of Beltran, as leadoff man Jose Reyes has battled injury and many of the team's established starters aren't hitting to their potential.
As a result, Manuel has decided Pagan is too valuable to the offense to be left on the bench. He has moved the 28-year-old switch-hitter to right field, and it looks as though Francoeur, a .300 hitter against lefties for his career, will be used only against southpaws, though not necessarily every time they face a left-hander.
"It's kind of a situation, I don't know how to describe it because this is the first time it happened to me," Pagan said. "But I'm playing right field every day. That's Jeff's position. He was there, but I can tell you he's going to be out there too. We're all going to help the team as much as we can. It's just a matter of helping each other, pushing each other."
The competition and consistent playing time has allowed Pagan to blossom, creating a fragile situation for Manuel, who regularly reminds the media that he is "not a stats guy."
But Pagan's manager sees the same thing as all the sabermetricians.
Pagan has gone from replacement player to irreplaceable.
Kyle Maistri is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.