"He was up and hot already."
I don't really get it, but relievers don't like to get warmed up and not used in that night's game. Managers also seem to consider that a bullet fired anyway, so if you're odds of treating him as available for Sunday had already been reduced simply by having him warm up, I guess you might as well use him in tonight's game.
I oversimplified. But this doesn't address the additional point that Parker was also warmed up (from having been used) and had thrown only 15 pitches.
Also, I have absolutely no problem with managers deciding things. Rocco has done a few things I've noticed, and doubtless many that I haven't, making a statement that this is his team. Good leaders do that. "I'm not the manager because I'm always right, but I'm always right because I'm the manager." -- Gene Mauch
Rocco is the anti-Gardy in regard to closer usage. At a BoSox game I attended earlier this year, sitting next to the visitors bullpen, Shane Greene was up and fully warmed up, then his Tiger teammates scored a couple of runs making it no longer a save situation; down he sat and another guy who had been warming up came in. The chump allowed enough runs to make it a save situation again, so in came Greene. Nothing remarkable about that, but I suppose times are changing.