And Griffin hasn't just gotten to the big leagues -- he's excelled.
The 24-year-old is still without a win after three Major League starts, but that's through no fault of his own. In his first start, Griffin was thrown right into the heat of the Bay Bridge rivalry, but allowed just two runs to the Giants in six innings. In his next outing, he shut out the mighty Rangers for six innings, and he allowed one earned run to the Red Sox on Wednesday in another six-inning start.
Such a strong opening for a player who began the year in Double-A might surprise some, but not the ultra-confident Griffin.
"Everybody's different, but he's definitely on the upper end of that level of having confidence," said Craig Lefferts, Griffin's pitching coach at Single-A Stockton.
It's that extreme self assurance that's allowed Griffin to adhere so strictly and so well to his pitching philosophy, which is to "detach from consequence," in his profound-sounding words. It's also allowed him to shut out the distractions around him, like the raucous, half-Giants crowd in his Oakland debut. A's manager Bob Melvin said such composure is impressive for a young player.
"Just try to execute the pitch that I'm trying to do, and if I execute it and they hit it, I tip my hat," Griffin said. "If I don't execute it and they hit it, I mean that's on me, but at the same time, nobody's perfect, so you just go out there and try to get the next guy."
This unflappability and resiliency stems from Griffin's days as a closer in college.
Thrown into the bullpen as a freshman because the team already had a strong staff [led by former Orioles top prospect Brain Matusz and current Yankees prospect Josh Romanski], Griffin suddenly was faced with pitching in tense, nerve-wracking situations, which forced him to develop a "heightened sense of awareness and focus."
While playing for the Toreros, the righty also encountered the first real adversity of his career. As a junior he both closed and started, and while his numbers were solid, the sudden switch meant his arm wasn't in starting shape. He had to learn how to fight through innings with a fastball that sat in the underwhelming 84-88 mph range.
Those experiences served him well last year in his first full season of pro ball. Griffin quickly made it to Double-A Midland by the middle of the season, but found that hitters there were much more patient and polished than the lower levels. Lacking overpowering stuff, he wasn't finding success trying to strike everyone out, which had worked before.
Sent back down to Stockton, Griffin worked with Lefferts and others on changing his approach. He stopped trying to do too much. Instead, he focused on pounding the zone and keeping the ball down, and on pitching to contact more.
"When he came back, he just got back to what he does well, and that's mainly what we talked about, don't try and do more than you're capable of," Lefferts said. "It got him back to an area where he can execute his pitches, and that's the bottom line for him."
And while Griffin is defined on the field by his confidence, he isn't exactly withdrawn off the field, either. In fact, he is certifiably goofy.
Teammates call him unpredictable and talkative, and Griffin is certainly eclectic. He speaks Spanish (growing up in Southern California, many of his friends spoke the language) and French (an ex-girlfriend was from Paris). He plays the guitar, watches food shows and counts traveling and learning different cultures among his interests.
A's left-hander Sean Doolittle was Griffin's roommate for just a brief period in Triple-A Sacramento, but it was long enough to make an impression.
"There was never a dull moment," Doolittle said. "There was very little quiet time, I guess. He's a lot of fun, man. He's a high-energy guy. He's always talking about something, and it's not always in English."
To get himself amped up before outings in the Minors, Griffin -- who had control of the stereo system since he was starting -- would blast his strange mix of electro music and radio hits, moving/dancing around the clubhouse until he had nearly broken a sweat.
"We were all like, 'Who is this guy?'" said A's infielder Brandon Hicks, who played with Griffin at Sacramento. "We didn't really know him or how he was, but it makes sense. [He has] confidence in a good way.
"You shake your head at a few things, but it's just who he is."
Teammates say he's toned down the pregame routine since being called up, perhaps to avoid ruffling any feathers. But he's still bringing the same personality to the clubhouse every day. To point, a smiling Melvin was rendered speechless when asked to describe Griffin before a recent game.
For sheer force of personality, there may not be another rookie that can equal Griffin, and he's making quite the impression on the mound, too. In the early days of his big league career, he has nothing to complain about.
"It's even better than I thought it would be," Griffin said of his Major League experience. "It's kind of indescribable. The only care you have in the world is playing baseball."