"I'm feeling good, and the doctors say I'm doing really well," she said. "That's important, because this is the one last thing they could do to stop it."
Casey, 26, was diagnosed with acute lymphocytic leukemia in fall 2007. Twice she had relapsed, which led to the Jan. 25 bone-marrow transplant from an unknown donor in Europe.
She will spend the coming months in virtual isolation to prevent infection. She wears a mask whenever she is outside. All of her food must be well-cooked, including fruits and vegetables. She returns to the hospital three times a week to have her blood checked.
Casey is staying in Menlo Park temporarily, because she needs to be close to the hospital if she becomes ill. But she can again see their two young children — Savannah, 4, and Robert Jr., 3 — as long as they are healthy.
"She's looking great now," Guerrero said. "But my father was really tripping out when he saw her right after the transplant, because she was at the worst stage. He just turned to me and said, 'So you think you're a fighter? Now Casey is a real fighter.' "
Guerrero, 26, temporarily threw in the towel on his boxing career to be in her corner. He was supposed to fight Australian Michael Katsidis in an HBO bout March 27. It would have meant a payday in excess of $100,000 for Guerrero (25-1-1, 17 knockouts) and was envisioned as a springboard to more high-profile bouts.
"I was just worrying about so much," Guerrero said. "When I was in the gym, I couldn't relax, because I knew I had to get back to the hospital when the doctors were there. I was thinking about the kids all the time. I was just getting pulled in a million directions."
So he gave up the fight and also relinquished his junior-lightweight world title (130 pounds).
Shelly Finkel, Guerrero's co-manager, is a veteran of the fight game. He has never heard of a boxer canceling a main event to be with an ill wife.
"But I also can't imagine a young man with two children having his childhood sweetheart be this sick so early in their lives," Finkel said. "It's a big burden, but he had no choice. He's not the type of kid to run away from responsibilities."
Even Casey was a little surprised "... but thankful.
"I was so scared," she said. "I didn't know what to expect. I was happy that he could be there all the time with me. This is just the way Robert's always been. He's all about taking care of me and taking care of the kids."
Guerrero finished his workout with a long session on the heavy bag. Between punches, he talked about being taught how to help take care of Casey's medical needs. He even joked that he would like to receive a certificate proving he was "Stanford-educated."
But Jerry Kissee said he calls Guerrero "Doctor." One night, Guerrero had gone home to be with the kids when Casey called and said she was having trouble with a catheter. Guerrero got right back on the road to help her.
"He's such a nice person, and he's so in love with my granddaughter," Kissee said. "How can you not admire a young man like him?"
The gym sessions are mostly a stress reliever for the boxer. But if Casey continues to improve over the next month, Guerrero might resume serious training. For now, he's taking it one day at a time.
"Everything can change quickly, so the focus is still on her completely," he said. "But maybe pretty soon she'll want me to get out and go fight somebody. But I really don't want to go back into the ring until Casey can be right there watching."