Just because I enjoy a good discussion, allow me to point out that so far Kimbrel has 5 saves in 1 run games and 1 loss and 1 blown save. I'd call that 5-2, and the team is 21-8.
He has an ERA of 1.42, which is excellent, but it's for 12 innings. Velazquez has pitched 22 innings with a 2.05 ERA, Sale 42 innings with a 2.14, Porcello 40.1 with a 2.23 ERA, etc.
Those numbers tell me Kimbrel is the guy for the 9th, but the team needs a whole lot of help in the other 8 innings, to say nothing of the guys driving in and scoring the runs. The starting pitchers, I hasten to add, normally go thru a lineup at least twice and usually three or four times, but not Kimbrel. On the other hand, he must be ready for that one inning and can't afford to have it be a bad one.
In the end, I probably go by WAR, as clumsy as that is.
Right now Kimbrel's is .9, Velazquez 1.0, Sale 1.9, Porcello 2.0, and Price .8. Key lineup player WAR's are: Betts 1.7, Martinez 1.2, Bogie .8 (less than half the games).
The only salary bargain among the above is Velazquez. Sale, Porcello, and Price are all pricey, and so is Martinez. Betts and Bogie will be.