You have to count the losses we'd have when Whitlock pitched well in long relief or as a starter. Subtract those from the projected wins we'd have with him closing, assuming he did very well in the closer role.
I'm not doubting we'd have been better, but we can never know. It's a trade off.
The fact that we lost many games where Whitlock pitched well in long relief or as a starter does not take away from the fact that he helped put us in a position to win, and a weak closer lost those games.
Flip the roles, and maybe Whitlock never gets that many save opportunities, because the new long man is coughing up dingers, left and right, and we're down 6 by the 8th and 9th innings.
We are 6-4 in games Whitlock has pitchers, and in all but 1 of those wins, he pitched very well. (That was his last start.)
In the 4 losses he pitched in, he blew one save and started 3 games, where he allowed 3 ERs, total! It's hard for me to look at those 3 starts and say that because he we didn't win, he was misused.
We've had this running debate for a while, but IMO, Houck's profile fits the closer role better than starter/long relief, and Whitlock's fits the starter/long relief role better than Houck. Better than closer? Who really knows? He's dove very well as a starter and long man. Yes, this year, his numbers in relief are much better than as a starter, but most of those numbers were not as a traditional closer (1 IP, maybe a little more every now and then).