Since they are only one game behind the Atlanta Braves in the race for the NL Wild Card, the New York Mets are without one of their best offensive weapons.

On Monday, the Mets placed designated hitter JD Martinez on the paternity list and recalled outfielder DJ Stewart from Triple-A Syracuse. Martinez will be away from the team for up to three days as he and his girlfriend Brooke Wheeler await the birth of their first child.

The announcement comes as the Mets prepare for six home games, with the first series against Martinez’s former team, the Boston Red Sox.

Martinez, who signed a one-year, $12 million contract with the Mets at the last minute of spring training, has been swinging a great bat of late, posting a .308/.379/.577 batting average with two home runs over the last seven games. Despite batting with back problems and struggling after being signed late to the start of the year, Martinez has been a key performer in the middle of the Mets’ lineup. Overall, the veteran has posted a .777 OPS, hit 16 home runs and recorded 65 RBIs in 105 games this season.

To replace Martinez, the Mets brought Stewart back from Triple-A. Stewart was demoted to Syracuse when the Mets signed Jesse Winker at the trade deadline in late July. Since returning to the minor leagues, Stewart has posted a solid .879 OPS with two home runs and four stolen bases over the last 22 games.

The Mets will need all the help they can get this week if they want to continue to close the gap on the Braves. And it doesn’t help that Atlanta has two winnable series at home against the Rockies and Blue Jays.

Martinez can return as early as Tuesday, as the MLB paternity list allows players to play for one to three games.