Only if you push Brown out of the backcourt, which I'm not convinced is a net positive.
My short answer is
injuries happen, we will rarely have every player available.
Neither Brown nor Tatum minutes need to be affected with a healthy roster.
We had a full complement of healthy PGs in Oct/Nov/Dec2017:
Rozier avg ~ 23.5mins/gm in Oct/Nov/Dec
Kyrie avg ~ 33mins/gm in Oct/Nov/Dec
Smart avg ~31mins/gm in Oct/Nov/Dec
Larkin avg ~11mins/gm in Oct/Nov/Dec
So long Shane, maybe cut Kyrie/Smart down to 30mins/gm. Rozier gets an easy 25-30mins/gm. With room to hand some of those to Gordon Hayward.
We can do the same exercise with Hayward. He will find some minutes out of an older Horford, Ojeleye (14mins/gm), Nader, older Baynes, Theis.
It is not a question IF injuries will happen, but a question of WHEN they will happen. Also, rested players = more efficient players in playoffs. The Celtics have to manage the roster for an extra 8 weeks of playoff basketball every year.