Why is your best 3-pt shooter on the bench when that's what you need for the last shot?

After Brandon Knight's ridiculous step-back jumper gave the Bucks a 96-93 lead last night, the Celtics had the ball with 6.7 seconds remaining in the game.  Brad Stevens called a timeout to set up a play, then here's what happened:

Instant reaction to Jae Crowder's miss was as follows:

There's a bit of a common theme here, huh?  On the floor for the last 6.7 seconds were Crowder, Evan Turner, Marcus Smart, Avery Bradley and Jared Sullinger.  As you can see in the above screenshot, Thornton is on the bench, ironically directly behind Crowder as the ball bounces off the rim.

Thornton is shooting 40.7 percent from beyond the arc this season--Crowder is .327, Turner .310, Smart .353, Bradley .356 and Sullinger .287.  So what's the explanation?

I'm not buying it.  If that's the case, why not sub in 6'4" Thornton for 6'2" Bradley?  Or how about going with 6'9" Tayshaun Prince?  Prince has actually knocked down 19 of 40 (.475) threes this season.  Rookie sharpshooter James Young is also 6'6", by the way...

Follow Mark Vandeusen on Twitter @LucidSportsFan