Gradi helped bring Powell through at Gresty Road.
"Nick Powell is a match winner," Gradi told MUTV. "He doesn't rely on other people to make the goals for him. He's not a six-yard box player. In fact, we've been trying to encourage him to get in that six-yard box more. But he picks the ball up, runs at people and finishes with a goal. He wins matches on his own.
"I used to watch him in Crewe's Under-16s, training on a Monday night, and he'd hit them in from everywhere. When he joined us and came with the first team, he was a little more reluctant to do that. Perhaps he lost a bit of confidence doing that and he was playing in a more central role for England, where he was passing the ball.
"We managed to persuade him not to do that if you can score. Don't become a 'steady Eddie' if you can become a special player. He scored a terrific goal at Wimbledon for us and it reminded us of the goals he used to score for the Under-16s, going on from there to score some terrific goals."