Sterling, who signed for City from the Reds last summer, struggled for form under Manuel Pellegrini and was frequently criticised for his mediocre performances last season.
However, this campaign he has already scored four goals and provided three assists for the Citizens and is working well to a proper game style under the guidance of Guardiola.
"I felt last season, watching him from the outside, he drifted away from what he is," Rodger said ahead of Wednesday's Champions League tie between Celtic and City.
"It wasn't all his fault. He went into a changing room full of mature players, but he needs coaching. If you can improve at 32 you can certainly improve at 21. I felt he went into a system which was flexible with players running and moving.
"And I could see it with his performances with England. He lost what he was which is a one-v-one guy who is dynamic and can take people on. He can press the game, can score goals and create goals. And he can work hard. I felt he drifted into being something he wasn't. But you can see him now working with a clear plan.
"When he was with me at Liverpool we played him on the sides and as a No10. He had defined, clear roles on what he should do and he was brilliant, absolutely brilliant. He could take on board tactical information, great.
"Now he is working with a clear way of working with a plan and you see the benefits.
"He's super-confident, look at his goal against Swansea at the weekend. He covered the ground so easily, produced a little step-over and finish. So he's back to being right on track again and it's great to see."