Ahead of today doubleheader against the Atlanta Braves, the Mets have activated Jeff McNeil from the injured list and have placed Robert Gsellman on the IL , retroactive to June 20, with a lat strain. McNeil will be on the bench for the first game and may start the second one. Stephen Tarpley will also serve as the 27th man for the doubleheader and will wear number 46. McNeil last appeared in a game on May 16, when he injured his hamstring in the first inning of the team game against the Tampa Bay Rays and landed on the injured list shortly thereafter. On the season, the second baseman was hitting with three homers, a 106 wRC+, and a 0. 3 fWAR. McNeil played in one rehab game for High-A Brooklyn, where he went hitless in two at-bats, and he collected six hits in 15 at-bats for Triple-A Syracuse in four rehab games there . He marks the first of the club core group to return from injury, with Michael Conforto and Brandon Nimmo hopefully not far behind. Meanwhile, Gsellman has taken McNeil place on the injured list. The reliever recently started the team Saturday night contest against the Washington Nationals in the second game of that doubleheader. He surrendered a leadoff home run to Kyle Schwarber and took the loss as a result. Luis Rojas specified that the right-hander has dealt with this injury in the past, and did not provide any further details on how long he might miss as a result. Tarpley will return to the Mets as the 27th man in the hopes of recording an out and eliminating of his infinite ERA. He has made several pit stops in New York this year, but his lone appearance resulted in him surrendering two earned runs without recording an out, which accounts for the unfortunate line he currently sports .