The Texans' star wide receiver and Titans cornerback slugged it out in the fourth quarter of the Texans' 20-0 victory.
Finnegan set off the brawl by jabbing at Johnson's neck and face mask at the line of scrimmage. Johnson ripped off Finnegan's helmet and landed at least two punches to Finnegan's head and neck. The two spun each other, and Finnegan tore off Johnson's helmet before players and referees intervened.
"He kept doing little things and I told him: 'Just because you're frustrated, you need to stop what you're doing,' " Johnson said Sunday. "I guess he thought it was funny."
"Did I want it to escalate into that? Absolutely not," Finnegan said Monday on a Nashville radio show. "The only thing that upsets me ... if you reverse that and it's me, I'm not at the radio show. I'm sulking because I got a game suspension. But you twist it and it's because it's me."
The usually soft-spoken Johnson caught nine passes and a touchdown before being ejected.
"It's just a buildup of things over plays," Johnson said. "I just lost my cool."
"At a point, he snapped and started throwing blows," Finnegan said of Johnson.
Finnegan also said he was conscious not to throw punches at the Texans receiver. "You do that and you're suspended, hands down," he said Monday.
"At the end of the day, I guess he got his money's worth," Finnegan added.
Johnson apologized for his actions after the game.
"I would like to apologize to the organization, our owner, and my teammates," Johnson said. "What happened out there today was not me. I just lost my cool and I wish that I could take back what happened, but I can't. It's over and done with now."
During his radio interview on Nashville's 104.5 The Zone, Finnegan said the only thing he would apologize for was waving at the Houston crowd as he left the Reliant Stadium field.
This is the second time the pair has scuffled. Last season, Johnson was fined $7,500 for taking Finnegan to the ground by the face mask.
The Texans (5-6) play at Philadelphia on Thursday, and were concerned that their Pro Bowl receiver might be suspended. Johnson was expected to be available to comment after an evening practice.
The Titans (5-6) host Jacksonville on Sunday.
Finnegan was fined for personal fouls in three consecutive games earlier this season and was warned by the league after the third incident to watch his behavior after the whistle.
"This is not hockey this is the NFL," Finnegan said Monday. "It's crazy to me to see people condoning this like I got what I deserved."
Titans coach Jeff Fisher, co-chairman of the NFL's competition committee, spoke with league officials earlier Monday. Fisher said in his opinion Finnegan didn't throw a punch, but did get Johnson's face mask.
"I have very strong opinions about the fact I think he should not be suspended," Fisher said of Finnegan. "As far as what the league decides to do, that's a league decision.
"It's an unfortunate thing that happens. You've got two very talented, good football players competing, and it's just very unfortunate. It's not good for our game and I'm just disappointed that type of thing happens on the playing field."
ESPN.com's Paul Kuharsky and The Associated Press contributed to this report.