In an interview with CampusSports.net, Mettenberger opened a new door in the back-and-forth between the AFC South rivals.
"J.J. had to say it's a bit high schoolish that I take selfies, and I think he still rags me on Instagram every time he posts a selfie," Mettenberger said. "At the same time, if that's high schoolish, he got a letterman jacket made -- a Texans letterman jacket.
"That's pretty high schoolish to me, don't you say?"
A photo of Watt in his Texans letterman jacket circulated online in October after Watt took multiple digs -- in-game and after -- at Mettenberger's plethora of published selfies.
On Wednesday morning, Watt tweeted this thought.
A lion doesn't concern himself with the opinions of a sheep. Time to attack the day.— JJ Watt (@JJWatt) July 8, 2015
The letterman's jacket in question was issued to Watt as part of a Texans team function during the 2012 season.
The jackets, a brainchild of former Texans Shaun Cody and Connor Barwin, arrived when the Texans were 11-1 and on their way to New England to play the Patriots. The players wore the jackets to the game before losing 42-14. They haven't worn the jackets as a group again.
Last season, Mettenberger, displaced as the Titans' top quarterback when they selected Oregon's Marcus Mariota second overall in this year's draft, took and posted several photos of himself to social media during the week leading up to his first NFL start.
Mettenberger posted one to Twitter 90 minutes before the Titans' Week 8 home game against the Texans, a tweet that was brought to Watt's attention pregame.
After Watt sacked Mettenberger, Watt celebrated by miming as if he were taking a photo of himself. During his postgame news conference, Watt said the celebration was a reminder to Mettenberger that "this is the National Football League, not high school."
In the interview with CampusSports.net, Mettenberger chuckled as he offered an explanation for his selfie-taking behavior during the week.
"I got set up by a couple of my friends, sent a selfie out, it got leaked to the public," Mettenberger said. "Then ESPN asked me to send a selfie to them pregame. It just got blown up."