Here's what the timeline of substitutions looks like.
With 7:50 left, DJ White enters the game for Jason Terry between Pierce free throws.
At 7:46 left in the 4th and the Celtics down 95-77, Shavlik Randolph enters the game for Paul Pierce, joining Williams, Crawford, Green, and White.
This lineup stays together until 2:36, when Bass comes in for Randolph with the score 100-91.
Bass-White-Green-Williams-Crawford is the lineup until 23.3 left, with the score 104-100. After a Boston rebound and timeout, Pierce and Terry come in for Williams and White, an obvious move to put better shooters on the floor.
At 0:18.9, as Crawford shoots free throws, Williams and Bradley come in for Terry and Bass, an obvious move to put in defenders who can force a turnover.
Crawford commits a foul at 0:18.5 and Bayless shoots two. Bass and Wilcox come in for Crawford and Williams, an obvious move to put in bigger guys who have a better chance of rebounding a possible missed free throw. (Bayless makes both.)
The Celtics call timeout and Terry and Crawford come in for Bradley and Wilcox.
After Green gets fouled at 0:14.7 and goes to the line, Williams and Bradley come in for Pierce and Terry. Once again, Terry goes out and defenders come in.
At 0:12.1, Z. Randolph is fouled. Wilcox comes in for Crawford between free throws. If you lost track, the Celtics on the floor now is Wilcox, Green, Bradley, Williams, and Bass.
After Randolph makes his pair, the Celtics are down 108-104. The Celtics once again make a standard offense-for-defense substitution, bringing in Pierce, Crawford, and Terry and sending Bradley, Wilcox, and Williams.
Terry shoots free throws at 0:08.3. Since Terry is shooting, he can't come out, but Doc still makes the defensive substitution of Williams and Bradley in for Pierce and Bass.
Green fouls Conley and at 0:06.6, Doc makes his final substitution of Pierce for Williams, so that he as Green, Pierce, Bradley, Terry, and Crawford out there for the last few ticks.
So, between 7:46 and 0.23.3, Doc mostly let the bench play, with his only substitution being Bass for Randolph. After that, the game became a bit of a free throw shooting contest with a lot of stoppages due to foul and Doc made a lot of conventional offense/defense substitutions.