The Braves signed the 33-year-old Loney to a minor league deal on Thursday after learning their top player, Freddie Freeman, will miss about 10 weeks with a fractured left wrist.
Utility player Jace Peterson, who had no previous experience at first base, is making his second straight start at the position in Friday night's game against Washington.
Peterson could be a short-term replacement.
Manager Brian Snitker says if Loney earns good reviews in a few games with Gwinnett "we'll fire him in here."
Loney hit .265 with nine homers in 100 games for the Mets last year. He was released from a minor league contract with Detroit on May 7.
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