Burres, who made 20 appearances for Pittsburgh in 2010, was non-tendered by the Pirates on Dec. 2. That removed the left-hander from the 40-man roster, though general manager Neal Huntington said at the time that the club was interested in bringing Burres back.
Burres went 4-5 with a 4.99 ERA in 20 games (13 starts) last season.
Pittsburgh now has 15 non-roster invitees set to compete for roster spots beginning in February.