For my own benefit, I compared the stats, impact, and overall role to other players in the NBA, in order to get an idea of what a team of comparable non-celtics would look like. Based on my research for their play this year, this is what I found. At times I used per36 numbers to account for playing time. I know this isn't perfect, but don't nitpick.
Jeff Teague (Terry Rozier)
Otto Porter (Jayson Tatum)
Jonathon Simmons (Jaylen Brown)
Zaza Pachulia (Aron Baynes)
Nene Hilario (Greg Monroe)
Isaiah Canaan (Shane Larkin)
Quincy Acy (Semi Ojeleye)
Patrick Patterson(Yabusele)
What would that team win? With CBS as their coach, I think that team would be just under .500 and vying for one of the last playoff spots.
Obviously we hope that Brown, Tatum, Rozier, Ojeleye, and Yabu surpass the production and impact of their counterparts in the 2018-2019 season, but as far as this season goes, I definitely don't see a 50 win team.