Privately, he was livid, sources say -- enough that he initially wanted Mallett gone immediately, as the Houston Chronicle reported.
But the Texans opted to retain Mallett, given that they had only one other quarterback on the roster: starter Brian Hoyer.
O'Brien said Monday afternoon that he and Texans general manager Rick Smith were discussing options for how to handle Mallett's situation. O'Brien has control of the Texans 53-man roster, but on big decisions, the Texans seek a consensus.
It's still possible the Texans release Mallett, but they likely would need to find another quarterback first. The Texans' 2014 fourth-round pick, Tom Savage, is on injured reserve, and Zac Dysert is on the practice squad.
Mallett, who blamed his tardiness on traffic, was late for meetings Saturday, then missed the team's charter flight to South Florida. It was the second known time Mallett was late for a team activity.
Two days after O'Brien declared Hoyer the team's Week 1 starter, Mallett missed a practice. He told the Texans he overslept but he bought an alarm clock and it wouldn't happen again.
The Texans signed Mallett this offseason to compete with Hoyer for the starting quarterback job. Hoyer initially won the competition, then was benched in the fourth quarter of the Texans' season opener.
Mallett took over and then started four games in which the Texans went 1-3. Hoyer replaced him in the third quarter of a Week 4 loss to the Atlanta Falcons and in the second quarter of a Week 5 loss to the Indianapolis Colts.
Hoyer regained his starting job in Week 6. After the Texans beat the Jaguars in Hoyer's return, O'Brien said the team would stick with Hoyer.
Mallett had a guarantee of $1.75 million this season. He has no guaranteed money next season, which would be the final year of his deal, if the Texans retain him.