Obviously most of these guy are simply not expected to pitch again after they've sat down, with some exceptions (I.e. they will push Alvarado. They used to push Strahm and Hoffman more when they weren't at the top of the chain). Kerkering was probably ready to pitch the entire 7th if needed, but not the 8th. They also know which batters to prepare for ahead of times. And this point we also lack the match-up information (I.e .it's not just about LHP vs. LHB etc. but also pitch selection and swing paths). Thomson might have also been anticipating a PH that would have forced Kerkering to face someone he didn't want.
Romano of course, was a closer pitching in a non-save situation, they hate that 
On the bright side Kerkering should be available today. Romano and Strahm won't be.
