This will feel like 2021
The addition of Keene tells me that Bryce Underwood is going to play next season, a lot. That doesn't mean that he will start a game, but I do think a Cade McNamara-J.J. McCarthy time split like we saw in 2021 is possible, even likely.
Underwood has elite arm talent. However, some forget that his 247 Sports player comparison is Vince Young. That's because the dude can run, just like J.J. McCarthy (probably better). Michigan football limited McCarthy's runs, especially after he became the full-time starter, but it was a weapon.
Underwood will probably have a package similar to that of McCarthy. You'll see it expand as the season goes along and depending how the season goes, Underwood could see more playing time as the season progresses.
For McCarthy, that 2021 season was critical for his development. He played in every Big Ten game and had multiple Big Ten games with a rushing and passing touchdown, including the win at Wisconsin (and Maryland). McCarthy also had a touchdown pass against Michigan State.
Underwood should have a similar role and hopefully, it will yield similar results. The 2021 team was able to rebound after a disappointing season and McCarthy played a role in that, while also preparing to take over as the full-time starter, which he did in 2022.