Wow! Took a chance there, but that's why these guys run out from everywhere...
I looked and looked at the diagram trying to figure out what his intention was playing that 4 ball, and I'll bet money he wasn't expecting to thread the needle between the 15 and the 8 to nudge the 6 out (even though he must have been fully aware that the possibility was there).
I think he was trying to catch the 8 fuller and send it toward his balls. That way he opens up lanes to deal with his problem balls (3 and 5) and possibly would send the 8 into the 6-9 cluster. But even if the 6-9 were still clustered, he'd have plenty of opportunities to break it out if he could land the cueball in the patch where the 8 was.
That way he'd have the chance to run out with a little bit of a roll, but he could also protect himself if the pockets available for the 8 were blocked by his balls.
Does anyone agree?
VERY interesting decision making, right there...