The 23-year-old southpaw, who was acquired from the Padres in the New Years Eve Carlos Quentin deal, joins Jose Quintana, Dylan Axelrod, Eric Stults and Zach Stewart as injury replacements for the original starting five. Hernandez takes the spot of Gavin Floyd, who was placed on the disabled list for the first time in his career Tuesday because of right elbow tendinitis.
Hernandez produced a 7-2 record with a 2.90 ERA over stops with Double-A Birmingham and Triple-A Charlotte, and has made starts in 13 of his 14 overall appearances. He will be the 10th rookie pitcher to spend time on the 2012 White Sox roster.
"We go through Spring Training and he and [Quintana] were kind of in the same role," said White Sox manager Robin Ventura of Hernandez. "So you're hoping to catch lightning twice."
There's a chance Hernandez won't be around long enough to make the same sort of huge impact as Quintana. With Floyd placed on the disabled list retroactive to July 8, he is eligible to come off July 23 at home against the Twins.
Floyd has every intention of making that start and hopes his right elbow cooperates.
"I haven't picked up a ball in a couple of days," said Floyd, who felt the tendinitis really kick in during his July 7 home start against the Blue Jays. "I don't know how it feels throwing a ball, but I've been doing treatment and just trying to give it some time to cool down.
"We have a lot of season left. I want to be there for the rest of the season and be strong and give my best effort out there without having any doubts whether something is going to get worse or something like that."
Treatment is on the docket for Floyd on Tuesday and Wednesday. He's going to throw on Thursday and then throw a bullpen session on Friday to get ready for Monday. Floyd doesn't look at this injury as much of a setback after an MRI showed no structural damage.
"These days off are going to be pretty important for calming things down," Floyd said.
"He checked out," said Ventura of Floyd. "You want these guys to be as healthy as they can when they go out there and have no doubts at all about what's going on physically."