Pedro has been rewarded following an outstanding debut season in which he was named Player of the Year after scoring 20 goals and providing nine assists across all competitions.
Delap, meanwhile, has been handed the No.12 shirt amid uncertainty over his Stamford Bridge future.
The striker scored only three goals in 47 appearances last season and has reportedly attracted interest from Como.
Delap prefers to remain in England and could consider Premier League offers before the transfer window closes.
Elsewhere, Wesley Fofana takes the No.3 shirt, while Morgan Rogers will wear No.17. Mykhailo Mudryk has been allocated No.33 after being cleared to return, with Cole Palmer now occupying the No.10 shirt.
The changes come as Chelsea prepare for their opening fixture under manager Xabi Alonso.