Ball joined on transfer deadline day from Manchester City and will be in the squad against the Saints - though he will struggle to force his way into the starting XI.
Posh scored five in midweek against Sheffield Wednesday so manager Darren Ferguson will stick with the front three of George Boyd, Craig Mackail-Smith and Lee Tomlin.
Fellow new signing Paul Jones will again be on the bench as cover for number one goalkeeper Joe Lewis.
Defender Gabriel Zakuani is still three weeks away from a return after dislocating his shoulder while striker Dave Hibbert also remains on the sidelines.
Hibbert dislocated his knee back in November and is still not fit enough to return.
Source: PA
Source: PA