Flores made the Mets' roster for Opening Day in 2015.
During the first week of the season, Flores struggled offensively and defensively as he made three errors and batted .158 in seven games.
In nine games after the opening week, Flores batted .364 with three home runs.
Soon thereafter, Flores was tied for third in all of baseball in errors committed with six.
On May 16, Flores became the first National League position player to hit a grand slam batting ninth in a National League ballpark.
The home run came off Milwaukee Brewers pitcher Matt Garza at Citi Field.
The home run was his second career grand slam.
On May 26, Flores at the time was tied for most home runs hit by a shortstop with Jhonny Peralta of the St. Louis Cardinals with seven.
That same day, Flores hit his first career walk-off, a single, off Phillies' pitcher Elvis Araújo in the bottom of the tenth inning with two outs scoring Juan Lagares for his second RBI of the game.

On July 29, rumors spread during a game against the San Diego Padres that Flores had been traded to the Milwaukee Brewers, along with pitcher Zack Wheeler, for Carlos Gómez.
Despite the rumors, Flores remained in the game, and was visibly emotional when he returned to the field as fans began to give him a standing ovation.
Flores later explained his disappointment in learning that he would be leaving the only baseball organization he has ever known.
However, following the game, General Manager Sandy Alderson informed the media that no trade had occurred, stating that "social media got ahead of the facts."
After the game, Mets' manager Terry Collins told the media that he knew nothing about the potential trade and had told Flores while the events played out, "Listen, I don't know what's going on, but you've got a game to play, let's play baseball."
It was later reported that the Mets backed out of the trade after a concern about Gómez's physical as a medical report showed an issue with his hip.

Two days later, on July 31, Flores hit his first career walk-off home run, a solo home run, off Washington Nationals pitcher Felipe Rivero.
It occurred in the bottom of the 12th inning, on a 1–1 count with no outs, winning an important game for the Mets by a score of 2–1.
As Flores approached home plate finishing his circle around the bases, he memorably tugged enthusiastically  at the "Mets" logo on his uniform front, signifying how happy he was to have remained with the team.
Flores had also driven in the other Mets' run earlier in the game.
During each at-bat, Flores received a standing ovation from the Mets' fans.
The win brought the Mets within two games of first place in the NL East.
After the incident, Flores became a fan-favorite of Mets fans and was given standing ovations in the subsequent weeks, both at home and at away games.
It was also the only walk-off home run the Mets hit during the 2015 season.
At this point on August 25, since the failed trade, he hit .343 with a .993 OPS and four home runs.
The Mets went 16–6 after that day.
Flores finished the 2015 season appearing in 137 games with a batting average of .263 in 483 at-bats in 510 plate appearances while compiling 127 hits, 16 home runs, 59 RBIs, 55 runs scored, 19 walks, and striking out 63 times.

In the NLDS against the Los Angeles Dodgers, Flores hit .300 in four games compiling 3 hits, 1 double, 2 walks, 2 runs scored, and striking out 4 times.
Then, playing against the Chicago Cubs in the NLCS, he batted .286 in four games compiling 4 hits, 1 double, 1 triple, 1 walk, 1 stolen base, and striking out 2 times.
During the series against the Dodgers, Mets' shortstop Ruben Tejada was injured by the Dodgers' Chase Utley.
The injury occurred with a controversial slide, thought dirty by many, and resulted in a broken leg for Tejada.
Flores played shortstop for the remainder of the postseason.
Once he moved to the more important defensive position, Flores played fine defense, but struggled hitting.
He was the last out of the World Series, striking out looking in game five against Kansas City Royals closer Wade Davis, to clinch the se
Flores made the Mets' roster for Opening Day in 2015. During the first week of the season, Flores struggled offensively and defensively as he made three errors and batted .158 in seven games. In nine games after the opening week, Flores batted .364 with three home runs. Soon thereafter, Flores was tied for third in all of baseball in errors committed with six. On May 16, Flores became the first National League position player to hit a grand slam batting ninth in a National League ballpark. The home run came off Milwaukee Brewers pitcher Matt Garza at Citi Field. The home run was his second career grand slam. On May 26, Flores at the time was tied for most home runs hit by a shortstop with Jhonny Peralta of the St. Louis Cardinals with seven. That same day, Flores hit his first career walk-off, a single, off Phillies' pitcher Elvis Araújo in the bottom of the tenth inning with two outs scoring Juan Lagares for his second RBI of the game.
On July 29, rumors spread during a game against the San Diego Padres that Flores had been traded to the Milwaukee Brewers, along with pitcher Zack Wheeler, for Carlos Gómez. Despite the rumors, Flores remained in the game, and was visibly emotional when he returned to the field as fans began to give him a standing ovation. Flores later explained his disappointment in learning that he would be leaving the only baseball organization he has ever known. However, following the game, General Manager Sandy Alderson informed the media that no trade had occurred, stating that "social media got ahead of the facts." After the game, Mets' manager Terry Collins told the media that he knew nothing about the potential trade and had told Flores while the events played out, "Listen, I don't know what's going on, but you've got a game to play, let's play baseball." It was later reported that the Mets backed out of the trade after a concern about Gómez's physical as a medical report showed an issue with his hip.
Two days later, on July 31, Flores hit his first career walk-off home run, a solo home run, off Washington Nationals pitcher Felipe Rivero. It occurred in the bottom of the 12th inning, on a 1–1 count with no outs, winning an important game for the Mets by a score of 2–1. As Flores approached home plate finishing his circle around the bases, he memorably tugged enthusiastically  at the "Mets" logo on his uniform front, signifying how happy he was to have remained with the team. Flores had also driven in the other Mets' run earlier in the game. During each at-bat, Flores received a standing ovation from the Mets' fans. The win brought the Mets within two games of first place in the NL East. After the incident, Flores became a fan-favorite of Mets fans and was given standing ovations in the subsequent weeks, both at home and at away games. It was also the only walk-off home run the Mets hit during the 2015 season. At this point on August 25, since the failed trade, he hit .343 with a .993 OPS and four home runs. The Mets went 16–6 after that day. Flores finished the 2015 season appearing in 137 games with a batting average of .263 in 483 at-bats in 510 plate appearances while compiling 127 hits, 16 home runs, 59 RBIs, 55 runs scored, 19 walks, and striking out 63 times.
In the NLDS against the Los Angeles Dodgers, Flores hit .300 in four games compiling 3 hits, 1 double, 2 walks, 2 runs scored, and striking out 4 times. Then, playing against the Chicago Cubs in the NLCS, he batted .286 in four games compiling 4 hits, 1 double, 1 triple, 1 walk, 1 stolen base, and striking out 2 times. During the series against the Dodgers, Mets' shortstop Ruben Tejada was injured by the Dodgers' Chase Utley. The injury occurred with a controversial slide, thought dirty by many, and resulted in a broken leg for Tejada. Flores played shortstop for the remainder of the postseason. Once he moved to the more important defensive position, Flores played fine defense, but struggled hitting. He was the last out of the World Series, striking out looking in game five against Kansas City Royals closer Wade Davis, to clinch the se
Wilmer Flores