"They gave up on me," Butler said after the game. "F—. It is what it is."
The Patriots cornerback, the hero of Super Bowl XLIX, played a bit on special teams in the second half but not a single down on defense.
Eric Rowe started in place of Butler on Sunday.
"It was a coach's decision. … I don't know what it was," an emotional Butler said as he walked toward the team buses with his family. "I guess I wasn't playing good. They didn't feel comfortable. I could have changed that game, though.
"I was just doing my job supporting my teammates. I had nothing but great things to say about the organization. Great organization. They gave me the opportunity."
When asked what is next for him, Butler, who will become an unrestricted free agent after the season, said he didn't know. "I ain't Miss Cleo," he said, "so I can't tell the future."
Butler played 97.8 percent of the defensive snaps in the regular season. He arrived at Super Bowl LII one day after the team, on Tuesday, because of an illness that he said had him at the hospital. He wasn't on the team's final injury report.
Defensive coordinator Matt Patricia said Butler was healthy, but matchups were the reason for why he wasn't on the field.
"We just played all the guys we could to try to help us win in whatever packages we had," said Patricia, whose unit primarily played a "big nickel" package with two cornerbacks and three safeties throughout the game. "Different situations came up, and we were just trying to move some things around. … We just had a situation where we had some matchups and packages that we went with."
"He did a good job of staying in tune the whole time, cheering his teammates on, so a lot of respect to Malcolm for being a great teammate today," Harmon said. "Everybody wants to play this game. Everybody works hard to play this game. I'm pretty sure that he was a little upset that he didn't play."
NBC asked Patriots coach Bill Belichick at halftime why Butler was not playing and reported that the coach said, "I made the decisions that give us the best chance to win."
After the game, Belichick said it was a football decision, not a disciplinary move.
"We put the players and the game plan out there that we thought would be the best, like we always do," he said.
Butler was visibly emotional during the national anthem and was crying on the sideline.
Because Butler has been a mainstay on defense, Devin McCourty said "to not be out there I'm sure crushed him," McCourty told the Boston Herald. "We all want to be out there, we all want to play, so I know Malc, he's super competitive. He wants to be out there, so I'm not surprised he was emotional."
Rowe, who at 6-foot-1 and 205 pounds is a bigger option than the 5-foot-11, 190-pound Butler, was in coverage on the Eagles' initial two first-down conversions. The second of those plays came on third-and-12.
Rowe broke up a pass in the end zone on the Eagles' opening drive to force a field goal but then was in coverage on Alshon Jeffery's 34-yard touchdown in the end zone.
Of Butler, Rowe said, "He's a very emotional guy. He has a lot of passion for the game. It is not often you go to the Super Bowl. I know he has gone a few times, but I feel for him."
Added Gilmore, the team's other starting cornerback: "He's a great player. He could have helped us, maybe, I don't know. That's how the game goes sometimes."
ESPN's Adam Schefter contributed to his report.