But don't try to tell the right-hander that this move is some kind of demotion.
"That's disrespectful to the guys who are in the bullpen to say, 'I'm good enough to start,'" said Humber. "Well, I'm hoping I'm good enough to be in the bullpen. That's the attitude I take as far as whatever role I'm given, whenever they give me the ball, I'm going to do the best I can with it.
"Like I told [White Sox pitching coach Don Cooper] the other day, 'If this is something that you guys think is best for the team, then I want to do it because I think our team is really good.' Every day I see something else that's, 'Man, that's another sign of a really good team.' I want to be a part of it in any way that they allow me to be because I think we're going a long way this year."
In order to give first-year starter Chris Sale and rookie Jose Quintana extended rest between starts, the White Sox briefly employed a six-man rotation after acquiring Francisco Liriano from the Twins on July 28. Sale worked Monday with nine days between starts, while Quintana will have eight days when he takes the mound on Wednesday.
Those long rest periods might become a thing of the past as the White Sox go to the whip over the season's final two months. Humber will be able to spot start, while Hector Santiago also is being stretched out at Triple-A Charlotte, getting his second start at Indianapolis on Wednesday.
"Listen, every role is important. There are no [garbage] innings," Cooper said. "We want them all filled with as much quality as we can get. We're lucky to have six starters. We're lucky to put one of those guys in the bullpen right now because we got a guy who can give us innings and it's going to take a bit of the load off somebody."
Playing close games, with the last seven contests decided by no more than two runs, have put more wear and tear on the bullpen than going with one less reliever in the six-man setup. Humber, who threw a perfect game on April 21 in Seattle but has allowed 59 earned runs in his last 73 2/3 innings pitched, will provide bullpen assistance.
"With having Phil down in the bullpen, you do have flexibility that if you need to he can start any time in case that you need a Major League arm," manager Robin Ventura said. "He's the best guy for it. It helps us a lot in the flexibility."
"Mentally, there have been some things I've come along out of the ordinary, and the results I've gotten on the field at times have been very frustrating to me," Humber said. "But nobody cares more than I do and wants to succeed when I go out there. I put as much effort as I possibly can to be good at what I'm doing."