Jarvis was in at the end against Toronto. Against the Clips the starters closed out the game +9. The Laker game was a blow out and the end didn't matter. I believe Simmons was in at the end against Sacramento because he is a much better rebounder than Jarvis at the PF position, which was where Frank had him.
Prior to Toronto, the Cleveland game was a blow out and didn't matter who was in at the end. In Atlanta Jarvis was in until he got hurt. Frank went with Anderson in place of Simmons in the home Atlanta game.
I'm not a big Simmons fan, but overall last night he had a +5 impact in the game and Hayes was a +1, thanks mostly to a +2 over the last 40 seconds after Carter got hurt and he was playing with Simmons. To start the 4th quarter the Kings went +3 and Frank made wholesale substitutions and kept only Dooling and Simmons and the Nets went +3. Then he subbed Harris for Simmons and the Kings went +6 over a good chunk of the 4th. He put Simmons back in for the last minute and the Nets went +5 to tie the score! We finished +2 in OT with Simmons. Frank must've seen something he liked with Simmons in rather than on the bench.
Hey we won and it's obvious there is no SF on this roster that clearly deserves minutes above any other. Looks like it's a matter of end game match ups and circumstances and since Frank studies the tendencies of everything during the game I trust him to make that call.
And one more thing... it wasn't Simmons fault that Harris was horrible for the first 47 minutes of the game. Think he went partying with the Laker girls the night before. Would've been a much easier game if he was remotely on.