Gilbride, who retired last Thursday following 10 seasons with the Giants, addressed several of the team's offensive issues Tuesday night during an interview with SiriusXM NFL Radio.
The Giants finished 28th in the NFL in total offense this past season, and the injury-plagued offensive line couldn't consistently protect Manning, who led the league with a career-high 27 interceptions.
"[The offensive line] made it impossible for [Manning] to function. ... You give him help and he's proven he can win a championship," Gilbride told SiriusXM.
Gilbride also said the Giants adjusted their offense to include more three-step drops and fewer of the five-step and seven-step drops that allow Manning to thrive.
"We had been concerned about depth in the offensive line for a while now," Gilbride said.
ESPN.com Giants reporter Dan Graziano contributed to this report.