Myler kicked over 20 points at Cardiff Arms Park as the Saints sealed a 30-16 victory to clinch the trophy.
"You need a performance like that in big games, just somebody who can keep their head to make really good decisions, not just kicking the goals," Mallinder is quoted as saying by Sky Sports News. "It was top-drawer by Stephen on a night when all of our leaders stepped up.
"Stephen kicked his goals - you have got to take your points in games like this. Unfortunately for [Bath fly-half] George Ford, he missed a few at a crucial time."
Northampton return to action next Saturday when they face Saracens in the Aviva Premiership final at Twickenham Stadium.