During the last three seasons, Citi Field has become the Mets' own house of horrors. While visiting teams have made themselves at home, the Mets have struggled to figure out their unfriendly confines.

They hoped that cutting down its cavernous dimensions might help, but the results remained the same. The problem has become so prevalent that Mets officials devoted part of this offseason to unlocking the secrets of their own ballpark.

So why is it that the Mets would have been better off spending the last three years on a barnstorming tour?

"I don't think there's a short answer, certainly not a clean one," Mets vice president Paul DePodesta said. "I think there are probably a lot of different factors at play. To the extent that each factor played a role, I couldn't put percentages on it."

General manager Sandy Alderson believes that enough was learned to begin an effort to reverse what has become a decided home-field disadvantage. The Mets intend to begin by changing up their preparation before home games.

"I don't think that we've reached any conclusions," Alderson said. "But there's things we're going to do a little bit differently in terms of pregame routine that more mirrors the timeline that we have on the road."

Perhaps that will be enough. But for the Mets to have any realistic shot of reaching Alderson's 90-win goal, the effort must begin at home.

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Since 2011, the Mets' .424 percentage (103-140) at home ranks 28th in the big leagues, better than only the Twins and Astros. It ranked far below the big-league average of .509. But in that same span, the Mets posted a .502 percentage (122-121) away from Citi Field. That's easily above the .491 road winning percentage posted by all teams in those three seasons.

The Mets' home-field struggles look even more amplified when compared to their relative success on the road. In the last three years, nine big-league teams have had losing records at home. Of that group, only the Mets have posted a winning mark on the road.

Drilling down on those numbers presents a bleak picture of the Mets' incompetence on their own home turf.

On the road in the past three seasons, the Mets have scored 1,104 runs and posted a healthy .719 OPS, the eighth-highest total in baseball, just one spot behind the Yankees. But at home, the Mets' total of 883 runs ranks only 26th and their .679 OPS is 28th -- a 40-point drop from what they have produced in visiting parks.

Citi Field has become a much more forgiving park for home- run hitters since the fences were moved in before the 2012 season. But the cozy dimensions have proved to be far more friendly to the guests than they have been to the hosts.

In the last three years, visiting teams have made themselves feel right at home, bashing 236 home runs at Citi Field. That figure dwarfs the 176 the Mets have slugged on their own field.

"If you get outhomered anywhere, you're usually going to lose," DePodesta said. "So we had to address that."

The Mets coveted power in the offseason, leading to their signing of Curtis Granderson to a four-year, $60 million deal. They also gave Chris Young a one-year, $7.25 million contract, taking a chance on him because of his track record despite a down year in 2013.

But an infusion of power represents only a small piece of the puzzle.

Team insiders said that during meetings, multiple factors were discussed, ranging from the composition of the outfield to the kind of food served to the players before home games.

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"For me, it was all about athleticism," said one official, who noted the Mets' overall improvement after Juan Lagares helped to vastly improve the team's outfield defense.

The possibility also exists that the Mets' struggles at home may simply be a matter of chance, a cruel coincidence. Yet for all of the theories offered, DePodesta said none could be identified as the definitive cause.

"I don't think there's a silver bullet here, one thing," he said. "I think it's probably a confluence of a number of different factors, one of which is coincidental outcomes. Now, is that 10 percent of it? Is it 60 percent? I don't know."

So in the absence of conclusive evidence, the Mets have shifted their focus toward improving their daily preparation.

In the past, to snap his team out of losing skids at home, manager Terry Collins has made small adjustments to how the Mets get ready for games. But this season, the Mets appear ready to adopt that idea on a grander scale.

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Team officials have been hesitant to share their planned changes because some of the details have yet to be hashed out. But the Mets have examined ways to limit distractions before games, when players often can be pulled in different directions.

Mets officials also have looked into tightening access to the clubhouse and adjusting the structure of the day leading up to first pitch, whether it be when players begin their stretching routines or start batting practice.

The hope is that some of the changes might cut down on the down time between activities -- similar to the condensed schedule that a team endures when playing in a visiting ballpark.

Ultimately, Alderson believes the most meaningful changes might have nothing to do with the size of the ballpark, the composition of the roster or the structure of the workday. Instead, turning around some of the Mets' struggles at home may simply be a matter of mentality.

"It's also about changing the mind-set, recognizing that we've had issues and affirmatively thinking about changing those results," Alderson said. "So it's not just about routine, it's not about anything physical necessarily. It's about also being a little bit better prepared mentally."

Of course, when it comes to unlocking the riddle of Citi Field, there appears to be few straightforward answers.

"It's hard to quantify how the environmental actually impacts the mental," DePodesta said. "I think there's some interplay there. There's a lot of gray area."