As Phil Humber prepares to face the Twins on Thursday night at U.S. Cellular Field, the White Sox still hope he is added to the All-Star team.

If that thought makes your head spin, Humber knows the feeling. In fact, when he looks back on his 18 months with the Twins, he often thinks about something pitching coach Rick Anderson told him during a mound visit.

"Andy said, 'It looks like your mind's spinning,'" Humber said. "I just got so worked up trying to do well that I would lose sight of what I needed to be focused on, which is getting your pitches over the plate."

When Humber, 28, explains this year's sudden success, he talks a lot about his mental transformation. Sure, White Sox pitching coach Don Cooper helped him develop a slider, but it has taken more than a new pitch to go 8-4 with a 2.69 ERA.

The White Sox grabbed Humber off baseball's scrap heap in January. He had been discarded by the Mets, Twins and Royals.

The Twins acquired him in the 2008 trade that sent Johan Santana to the Mets. Humber spent most of his time with Class AAA Rochester and posted a 6.10 ERA in 20 relief appearances for Minnesota.

"In 2009, I made the team out of spring training, and I didn't even want to be here," Humber said last month at Target Field. "I mean, everyone wants to be in the big leagues, but when things are going like that, it just isn't fun.

"I'm in the bullpen, hoping the phone doesn't ring for me because I'm afraid of what's going to happen. I'm so wrapped up in the results that I can't even enjoy myself."

It's easy to understand why Humber put so much pressure on himself. The Texas native helped pitch Rice to the 2003 NCAA title, and he was one of three pitchers from that team who were drafted in the top eight overall in 2004 -- Humber went third to the Mets; Jeff Niemann went fourth to the Rays; and Wade Townsend went eighth to the Orioles.

"[Humber] was consistently good from Day 1," Niemann said. "He came in and was a weekend starter as a freshman, All-American, Team USA, everything. He struck out 16 in a game once, a Rice record. It was so fun to watch."

Being part of the Santana trade only added to the expectations. The Twins let him leave as a free agent after the 2009 season. He signed with the Royals and spent most of last year at Class AAA Omaha. One night, with his wife watching from the stands, he got hit near the mouth with a line drive, requiring 18 stitches.

"It was just another way of God showing me, 'Don't hold on to that too tight because life can be snatched from you in an instant,'" Humber said.

He wound up making eight appearances with the Royals late last season, and the White Sox saw enough to claim him on waivers.

Cooper suggested adding a slider or cut fastball to help expand the strike zone against righthanded hitters.

"It's really come a long way during the season," Humber said. "It's turned into more of a pitch than I thought it would be and taken pressure off my curveball, which is my main out pitch."

Humber has benefited from a .222 batting average on balls in play -- a mark well below the league average, which suggests his luck could turn the other way -- but last Saturday, he tossed seven shutout innings against the Cubs.

Humber hasn't been named to the All-Star team yet, but the White Sox remain hopeful because three American League pitchers -- Justin Verlander, Felix Hernandez and James Shields -- are scheduled to pitch Sunday, which would make them ineligible to compete in Tuesday's All-Star Game.

"If Phil Humber's not on the All-Star team, there shouldn't be an All-Star Game because he's been that good for us," White Sox catcher A.J. Pierzynski told reporters.

Joe Christensen jchristensen@startribune.com