Howell has worked only with the starters since spring practices began. He has taken all but several reps with the starters; Jacoby Brissett, signed in the offseason, took his place for a handful of snaps before the preseason opener against the Cleveland Browns.
"It means a lot," Howell said. "[But] all my work is ahead of me. This is only the beginning."
Washington hosts the Arizona Cardinals in the season opener Sept. 10.
Rivera said he met with offensive coordinator Eric Bieniemy and quarterbacks coach Tavita Pritchard on Thursday to discuss the situation. They all agreed this was the right move.
"This was about what Sam did," Rivera said. "Jacoby has been a true pro and done everything asked, and he's also helped mentor Sam. He's a more than viable quarterback. But there were certain things Sam had to show us, and everybody knew from my perspective it was Sam's to lose, and he did nothing to lose it."
Howell never did anything to lose his grip on the job. He completed 9 of 12 passes for 77 yards and a touchdown against the Browns. In the two-day joint practice session against the Baltimore Ravens, his performance on the first day was "really, really good," a source said. Howell wasn't quite as sharp on the second day, but the Commanders still liked what they saw.
"This is what I was anticipating," Rivera said of Howell's camp. "It's what we all were looking for."
Rivera had pointed to this past week as a crucial one for Howell in measuring his development. After the second day, when asked what Howell needed to do to be named the starter, Rivera said, "Continue what he has shown."
"I wasn't worried about anyone else's expectations except for my own," Howell said. "I have very high standards for myself."
The Ravens had a top-10 defense last season, providing a good test for Howell and the offense.
"After the first practice, that was the high-water mark for me," Rivera said, "in terms of having to see and show us what he was capable of doing. A very good day. Watching the tape, I kept thinking to myself, 'That's what I wanted to see.' So I feel confident and comfortable enough to say Sam's our guy. There's still more growth to go. He'll continue to get better. We believe that."
The Commanders like Howell's decisiveness -- particularly when working through progressions and spotting an open target -- and his improved footwork on pass drops and handoffs. They like his decision-making. They say other aspects of his game, such as becoming more efficient in the red zone, can be developed with more experience.
"The biggest thing I'm really pleased about has been his decision-making; that has been a big plus," Rivera said Wednesday.
Washington drafted Howell in the fifth round in 2022, although one team source said before the draft that the Commanders would have targeted him in the second or third round had they not traded for Carson Wentz that offseason. When Howell, who started for three years at North Carolina, was still there in the fifth, they pounced.
He served as the No. 3 quarterback behind Wentz and Taylor Heinicke early in the season. When Wentz broke a finger in Week 6 against the Chicago Bears, Howell was elevated to the primary backup. That gave him more work in practice against the scout team. He stayed in that role until Wentz returned in Week 15.
However, when Washington was eliminated from playoff contention two weeks later, it started Howell in the season finale. In a 26-6 win over the Dallas Cowboys, who played their starters, Howell completed 11 of 19 passes for 169 yards and one touchdown and had one interception. He also ran for a score. Rivera said they liked how he handled his start, from his decision-making to his ability to self-correct any mistakes.
"It's a confidence thing," Howell said. "When I step on the field I'm confident in my ability, I'm confident in the offense, I'm confident in my teammates and I'm confident in the system. When I'm confident in all those things I can just go out there and play free and play fast. That's what I've been doing."
Early in the offseason, Rivera said that Howell would enter spring workouts as the No. 1 quarterback but that he still had to earn the job. The Commanders eventually cut Wentz and lost Heinicke to the Atlanta Falcons in free agency.
Rivera had said several times, "Don't sleep on Jacoby." But Howell played well enough that a true battle never materialized.
"Jacoby did some really good things too, so we feel really comfortable about the quarterback room right now," Rivera said.
Rivera said Commanders were "thrilled" with Howell's growth from the start vs. Dallas to the spring workouts and into training camp.
"He's in a really good spot," Rivera said of Howell's development. "He's now more than a serviceable quarterback. He's a guy that's growing. He's a guy that can win. ... I'm excited for it, excited for the team."