CHICAGO — Late Wednesday night, after the Mets’ celebration had spilled onto the field and players were milling about with their families, outfielder Curtis Granderson found first baseman Lucas Duda and took a short video of Duda with his parents.  Duda smiled momentarily before he playfully tried to take the camera away. Undeterred, Granderson turned it on himself and his teammate.  “We’re going to the World Series!” Granderson shouted.  For three months, Granderson had been taking pictures and videos of Duda without his permission and posting them to an Instagram account, @wefollowlucasduda. And this night was worth commemorating. The Mets had just swept the Chicago Cubs to clinch the National League pennant; Duda had been the star of Game 4, breaking out of a slump to drive in five runs; and Granderson, a Chicago-area native, had continued his solid play.  Until this postseason, before the national news media descended on the Mets to chronicle their first run to the World Series in 15 years, the best glimpse into Duda’s psyche came via that Instagram account. Granderson started it in July, along with his teammates John Mayberry Jr. and Danny Muno, because they thought that Duda was a popular enough player and that he should have one.  The notoriously quiet Duda disagreed. But as Granderson took control of the account and kept populating it with candid photos and videos, often ambushing Duda in humorous encounters when he least expected to be caught on camera, the account showed a looser side of Duda and, in the process, a funnier, less polished version of Granderson.  When Granderson posted the video Thursday, the account had nearly 50,000 followers.  The account started innocently enough, with photos of Duda putting on his uniform, Duda eating a salad, Duda napping in the clubhouse, Duda wearing sunglasses on a plane, Duda at his high school graduation, Duda wearing a cowboy hat, Duda smiling with a bouquet of flowers. One picture, of Duda grabbing a slice of cake, had the caption “The key to homers is red velvet.”  If that were the case, Duda might have tried eating red velvet cake in the playoffs.  Before his star turn in the clincher of the N.L. Championship Series, Duda was batting 3 for 24 in the postseason and had 13 strikeouts. He had kept his head down, mostly avoided the news media and worked tirelessly with the hitting coach Kevin Long. But Duda could not get the timing of his leg kick just right. He had hit 57 home runs over the last two seasons, and he knew he was expected to produce, so he kept piling pressure on himself. His parents were there supporting him, but even that did not help.  “My dad’s always positive,” Duda said. “My mom, she doesn’t really care if I struggle or not. She’s going to love me no matter what, I think. Or I hope.”  All season, Duda had been prone to slumps and hot streaks. He just happened to be caught in a slump at the worst possible time.  When he is struggling at the plate, Duda likes to be left alone, which is perhaps why he became annoyed when Granderson started taking videos of him. Granderson filmed Duda in the batting cage, playing with his glove at his locker stall, eating peach cobbler in the lunchroom. Granderson usually added a bit of comedy by narrating the videos as if he were a wildlife expert who had just come upon an exotic animal in its natural habitat.  Soon, the two of them developed a routine: When Granderson filmed Duda, Duda attacked the camera, sometimes smiling and sometimes not, like a celebrity swatting at paparazzi. Granderson responded by laughing it off. Once, when Granderson caught Duda lying on his back in the weight room, Duda hopped up and chased him as Granderson giggled.  “We’ve got him in some incriminating spots,” Granderson said. “He’s like, ‘My mom’s going to see that!’ I said: ‘Exactly! Your mom’s going to see it and love it!’ ”  But as the regular season wound down, Duda appeared to have reached his limit. Sitting in the lunchroom one day, he noticed Granderson filming him and shook his head, dejectedly.  “Curtis, get a life, man,” Duda said. “I’m tired of you filming me all the time.”  “No, you’re not,” Granderson replied, not missing a beat.  In public, Granderson rarely shows this side of himself. He is usually polite and accommodating, but he speaks in polished clichés, seemingly being careful not to say anything too inflammatory or out of line.  In these videos, though, Granderson is the prankster. His relatives and friends surely see that side of him more often. About 100 of them came to watch him play Games 3 and 4 of the N.L.C.S. at Wrigley Field. Some of them also gathered on the field and celebrated on Wednesday night, after Granderson had finished the first two rounds of the playoffs with a .303 batting average, seven R.B.I. and four steals in nine games.  This postseason has been validating for Granderson. The Mets signed him before the 2014 season to a four-year, $60 million contract to bring leadership and a winning culture to the clubhouse, and he has delivered. Several players cited Granderson and his even-keel demeanor as a calming influence. Even Duda seemed to eventually appreciate his videos.  In September, during the Mets’ first champagne celebration, after they had clinched a playoff berth, Duda willingly appeared in a video with Granderson. But Duda stood silently, with dark ski goggles on, and pretended to punch Granderson before finally giving a thumbs up.  A few weeks later, after the Mets won their division series against the Los Angeles Dodgers, Duda — even though he was slumping at the time — smiled with Granderson during another celebration video. As Matt Reynolds poured beers on them, Duda laughed and leaned his head back, soaking it all in. Just as the video ended, Duda put his arm around Granderson and looked as happy as could be.
Curtis Granderson, a teammate, has been posting photos and video clips showing Duda, a quiet slugger who ended a slump with five R.B.I. in Game 4 of the N.L.C.S., at unguarded moments.