Hyun-Jin Ryu's first major league appearance was...
He went 6 and a third innings. That's good.
He gave up 1 earned run. That's good.
He didn't walk anybody. That's good.
He struck out 5. That's good.
He induced 11 groundballs and only 3 fly balls. That's good.
He gave up 10 hits. That's not so good.
He only had a single 1-2-3 inning. That's not so good.
He gave up 2 unearned runs. Not so good.
The overall numbers on Ryu might look ok: 0 - 1 with a 1.42 ERA, 7.1 K/9 and a infinite K/BB ration. But we know he didn't pitch that well. Using Tom Tango's Batted Ball FIP, Ryu would have been expected to give up 3.64 runs per 9 innings. That's certainly doable. That's mostly due to the high number of groundballs (11 of 20 batted balls, 55%). 6 line drives (30%) is pretty high. That'll have to come down. Too many Giant hitters were squaring him up. If he keeps getting hit like that, he won't be successful.
Ryu faced 26 hitters and K'd 5 of them. That's 19%. The average NL starter (they get to face pitchers while AL pitchers face DH's) K'd 19.2% of the hitters they faced last season. So Ryu is right about average in that (through 1 game). The walk rate is great (through 1 game).
Ryu induced 9 swings and misses - 11% of Ryu's pitches induced a swing and miss. Major league average last year was 9%. Again, Ryu looks about average with his stuff.
Ryu threw 80 pitches. 55 were strikes. That's a 69% rate. All major league starters through strikes 63% of the time last season. Ryu threw a good number of strikes, not a great number. Not a number that would make one think that Ryu would go the entire season without walking a batter.
According to Brooks Baseball, Ryu threw:
43 4-seam fastballs. They averaged 89.2 MPH with the fastest coming in at 92.3 MPH
7 2-seam fastaballs. They averaged 89.5 MPH with the fastest coming in at 91.4 MPH
23 changeups. They averaged 80.8 MPH. That's about an 8 MPH difference from his fastball.
7 curveballs. They averaged 69.9 MPH.
The changeup was tabbed as Ryu's best pitch. He threw it 23 times and Giant hitters swung and missed 4 times (18%).
Felix Hernandez also has a pretty good changeup. Hitters have swung on and missed Felix's changeup about 20.5% of the time in his career.
So Ryu's not Felix Hernandez. I don't think anyone expected that.
Ryu looked like an average to slightly above pitcher with his command and ability to generate swings and misses. If he can continue getting ground balls that translates into a pretty good pitcher.
If he keeps giving up line drives it's going to be a rough season.