Barnett played 70 minutes against Gillingham, less than 24 hours after making his comeback from three months out with a knee injury as a 73rd-minute substitute in Posh's Championship draw with Charlton at London Road.
"Tyrone looked very good and I felt he did very well when he came on as a substitute for the first-team," said Peterborough manager Darren Ferguson.
"He is still short of match fitness so starting him might be a risk, but I need game-changers on the bench and Tyrone is capable of that."
Barnett created goals for Craig Alcock and Shaquil McDonald as Posh beat Gills 3-1. Jermaine Anderson was also on the scoresheet.