This will be determined by several variables. Obviously everyone being reasonably healthy is a must. Also depends on who the 5 starters are for the season. Marcus Smart is the easy answer but only under certain conditions.
I picked Baynes and Tatum because I think whichever doesnt start may be first off the bench with or before Smart. This of course is also dependent on Haywards readiness at the beginning of the season.
I believe Brad will give him (Gordon) plenty of run with different combinations of players at the beginning of the season to establish chemistry and determine our best rotaions.
Still not sure Smart will be first off the bench but it may be completely fluid depending on matchups.