Lewis, 28, spent three seasons with the Patriots, winning a Super Bowl in 2017. He signed a four-year deal with the Titans in free agency following the 2017 season.
"It's a real sweet win, you know, especially when you used to be there and they didn't want to bring you back," Lewis told reporters on Sunday, following the Titans' 34-10 win. "So, definitely real sweet. I'm happy my teammates came out and played, and I love those guys."
Lewis had 57 yards on 20 carries and two catches for 11 yards in the win. He referenced the Patriots not wanting to sign him to a lucrative contract after the upset.
"Hell yeah, it's personal," Lewis said. "That's what happens when you go cheap. You get your [expletive] kicked."
Lewis now has 666 yards from scrimmage and two scores on 147 touches this season. He had a career-high 1,110 yards from scrimmage and nine scores on 212 touches in 2017 for the Patriots.
The Titans face the Indianapolis Colts at 1 p.m. on Sunday at Lucas Oil Stadium in Indianapolis.