"I'm not playing well enough," he added when asked about his comment.
Roethlisberger threw five interceptions—two returned for touchdowns—in the Steelers' 30-9 home loss to the Jaguars.
As NFL Research noted, he is one of two players with a zero-touchdown, five-plus-interception game since 2014 (Ryan Fitzpatrick in 2016).
Roethlisberger might not have been as dominant as in the past, but he had performed well enough in the first four games of the season to lead the team to a 3-1 record. He had a 90.7 quarterback rating with six touchdowns and just two interceptions.
Sunday's struggles could be more related to the Jaguars defense, which entered the day leading the NFL with just 147 passing yards allowed per game. Opposing quarterbacks had just a 65.5 rating against this unit in the first four games.
Of course, Roethlisberger's words should not be taken lightly. He considered retirement before the start of this season and refused to commit to playing beyond the 2017, per Ed Bouchette of the Pittsburgh Post-Gazette.
The Steelers are still 3-2 after the loss and will have at least a share of first place after Week 5, but the 35-year-old quarterback is clearly not enjoying himself.