His counterpart, however, proved yet again that his Cy Young season of a year ago was no flash-in-the-pan deal, either. Not by a long shot.
In a highly anticipated pitching duel between Mazzaro and Giants righty Tim Lincecum, only Mazzaro made any major mistakes. Lincecum was flat-out dominant, going the distance in a 3-0 San Francisco victory that opened a three-game Interleague series at raucous AT&T Park.
"He's the real deal, that's for sure," Oakland catcher Landon Powell said of Lincecum, who gave up seven hits and walked one while striking out eight in his first complete game of the year. "He's got three very, very good pitches, and he commands them all."
One of those pitches is a knee-buckling curveball, which Lincecum used mostly as a show pitch. Another is a sinking, fading changeup that seemed to sink and fade more as the game wore on.
And then there's the fastball, which can make the other two seem downright unfair.
"He was throwing 95 in the ninth inning," A's manager Bob Geren marveled. "That speaks for itself."
Mazzaro, who won his first two starts after being called up from Triple-A Sacramento on June 2, scattered six hits and a walk while striking out four over six innings for his third consecutive quality start.
"That guy has good stuff," said Giants outfielder Aaron Rowand. "He's deceptive and has good movement on his fastball. He throws the heck out of the ball."
On most nights, against many pitchers, Mazzaro's outing would have been good enough to get a win.
Not against Lincecum, who improved to 6-1 -- and was right in the thick of things when Mazzaro wobbled for the first time since he took the East Bay by storm.
After Pablo Sandoval broke up Mazzaro's no-no with a bunt single to open the bottom of the fifth, Nate Schierholtz singled with one out and Mazzaro walked Emmanuel Burriss to load the bases for Lincecum.
"I thought that was a good walk," said Mazzaro, who liked his chances of either striking out Lincecum or getting him to bounce into a double play.
Instead, he fell behind in the count and tried to sneak a fastball over the outside half of the plate. It drifted back over the heart of the dish, and Lincecum, a left-handed hitter, punched an RBI single to center. Rowand capped the rally with a two-run single to left.
"With the bases loaded, the last thing you want to do is walk the pitcher," Powell said. "We were just trying to throw a fastball over the plate."
"I'm sure after two starts with not giving up a run," Rowand said, "He wasn't expecting the pitcher to break that up."
Obviously, the Giants were aware of Mazzaro's streak.
"It was gonna end sooner or later," Mazzaro said. "It doesn't make it any worse that it was a pitcher, but yeah, that's a pitch I'd like to have back. ... The pitches that made me fall behind, too."
The A's had their best chance to score in the fourth, but Adam Kennedy was thrown out at home while trying to score from first base on a double to right-center field by Jack Cust.
"He's tough," Geren said of Lincecum, "so when you get opportunities, you need to take advantage of it. But we didn't have many opportunities. Those seven hits we got really were scattered. ... He had everything working."
Despite the loss, Mazzaro was able to smile afterward. He took particular pride in dropping down a pair of sacrifice bunts.
"He's not an easy guy to bunt against," Mazzaro said.
And on nights like Friday, he's even harder to hit.
"Give [Giants catcher Bengie] Molina credit, too," Powell said of his own counterpart. "He called a great game. Lincecum's nasty, and they were mixing it up nice, doing a nice job of keeping us off-balance.
"Honestly, I never had a clue what was coming."