Head coach Tom Higgins said Calvillo's exact role is not yet decided.
But Calvillo will be an offensive coach and be involved in every part of the offence with the exception of the offensive line.
Jeff Garcia, who was brought on as a quarterback coach in 2014, won't return.
Ryan Dinwiddie won't be back as the offensive coordinator, but he will remain on the coaching staff.
The team has yet to hire an offensive coordinator. Higgins said he hopes to fill this position early in 2015.