Jagielka admits he had "mixed emotions" when hearing of Terry's decision to retire from international football last month.
He said: "If John was here, I would say exactly the same thing. I'm gutted as an England fan. He has been a fantastic player for England, he's put his body on the line for many years now but he had his reasons.
"It was his decision. He wasn't forced as in like a gun to his head or anything.
"But, if you look at it from a purely personal point of view, it was one less person to compete with playing for England.
"It was also an opportunity for me to try and go higher up the pecking order."