"I feel like I'm four innings through Spring Training," Bumgarner said after throwing 62 pitches -- 41 of which were strikes. "I don't feel very far off. … The results obviously weren't very good, but that's not what's important right now.
"The important thing to me is being healthy and stamina and arm strength and all that. I feel pretty good about it."
Bumgarner topped out at 92 mph from the first inning. He surrendered four runs in the first two innings before settling down for an eight-pitch third inning.
He threw 26 pitches in the first, allowing a leadoff double, hit batter, walk and sacrifice fly. He recorded his lone strikeout during a 19-pitch second inning. The southpaw allowed three runs on a pair of doubles, a single and another sac fly.
He surrendered a leadoff single in the fourth then retired the next two batters before departing.
Sacramento manager Dave Brundage said Bumgarner was rusty early but mixed in cutters and curveballs to slow down Fresno batters from getting ahead in the count.
"He looked fine the last couple innings and had a better angle on it," Brundage said. "I thought he was down in the zone more. Early on, he had some balls up early in the count. And they jumped on it."
Bumgarner's fastball was consistently fast, topping out at 92 mph. But it was his slider, he said, that demands more attention before returning to the Majors.
"The slider wasn't great," Bumgarner said. "Some were OK. Later on in the game, they got better. That's the one pitch that has to be a little better before we're ready. But it's close."
A crowd of 14,014 -- Sacramento's first sellout of the season -- showed up in Giants orange for his start. And Giants executive vice president of baseball operations Brian Sabean traveled to see the outing.
"It was pretty fun to be a part of and see, like baseball's supposed to be," Bumgarner said.
Though Bumgarner admitted he's itching to return to the Majors, his stamina and arm strength still need progress to compete with opposing batters in "midseason form."
"I can't go up there throwing 65 pitches," Bumgarner said. "That's not going to do us much good. I just have to make sure that we're ready to go once we're finished with this thing."
Bumgarner will make another rehab start Wednesday -- likely at Class A San Jose, with Sacramento visiting Albuquerque next week.
The 27-year-old said honing his mental edge is as important as velocity and endurance.
"Everybody is going to be razor sharp right now," Bumgarner said. "I've got to make sure I'm ready mentally and physically."