Pittsburgh currently has Tony Watson and Kyle Lobstein as left-handed bullpen options, so the additions of O'Flaherty and Luebke will create additional competition in free agency. Many lefties are available on minor-league deals at this stage of the offseason, and will likely sign in the near future.
O'Flaherty, 31, was recently said to be choosing between four teams, signaling that he received significant interest on the free-agent market this winter. He spent 2015 between the Athletics and Mets, posting a rough 8.10 ERA in that span after rehabbing from Tommy John surgery.
Luebke, 30, has spent his entire major-league career with the Padres, appearing in 55 games (25 starts) from 2010-2012. He has missed the last three seasons due to a pair of Tommy John surgeries, but may be ready to return in 2015 after drawing interest from many clubs, including the Blue Jays, this winter.