He won't take another selfie before this week's game.
Mettenberger, in his rookie season with the Titans, made the joking guarantee as part of an explanation about what he's learned since the Texans star defensive end taunted his propensity for pregame selfies.
"I was just addicted to it, I guess. I put myself in a rehab program,'' said Mettenberger, whose handful of Twitter self-portraits of his changing look before the Texans game went viral. "And now that I've quit I feel like I am a much better person."
Mettenberger, 23, has recently been finding his stride as a starting quarterback since Watt sacked him twice during Houston's 30-16 win on Oct. 26 -- and then added insult to injury by imitating Mettenberger taking a photo of himself.
In his first four NFL starts, Mettenberger has thrown for 1,103 yards and seven total touchdowns and has a QBR of 34.6, drawing praise from Watt himself on Wednesday.
"I think he's continuing to grow as he goes along," Watt told the (Nashville) Tennessean. "I think he gets a little bit better each game, and I think he's going to continue to go along that path. He's going to continue to improve. He's got a strong arm. He's a smart guy. He can do some different things. He's going to continue to get better, and I like the way that's been playing."
Watt also expressed surprise at all the media attention generated by his Oct. 26 comments that his sack dance was a reminder Mettenberger was in the NFL, not high school.
Watt told reporters Wednesday he didn't understand what all the fuss was all about.
"I think that definitely got blown up more than I expected it to be," Watt said. "I guess I should have expected it with today's world, but somebody asked me a question after the game and I answered it. That's all there was to it. It's football."
Watt shrugged off any talk about Mettenberger reversing course and sending out another selfie before the Titans' rematch against the Texans this Sunday.
"He can do whatever he wants to, that's fine," Watt said.