Dixon, 21, went over for a try in the 34-24 win at London in Round One, and he added two more in the come-from-behind win at home to Salford on Friday night.
Simmons told the club’s official website: “We spoke with Dicko at the end of last season and asked him to bring more to his game. He was a good steady first grader but wasn’t winning any Man of the Match awards, his defence wasn’t bruising and he wasn’t scoring enough.
“He’s now running better lines and angles and bringing grunt to his defence. Last week his attack was good but he was disappointed with how he defended. Well tonight he got both right.
“He is a tremendous young man and is getting the rewards for training hard.”
Dixon, who scored Saints’ first try in the 2010 Grand Final defeat against Wigan, will make his 50th appearance for the club if selected against Hull KR on Sunday.