Flaherty's debut with the Cardinals had a little bit of everything, from a 1-2-3 first inning to a second inning when the Giants roughed up the rookie for five hits and one big swing, a two-run homer from San Francisco shortstop Brandon Crawford.
"The first inning was probably the best that I felt," Flaherty said. "I came out and I was able to throw strikes and get ahead and really execute and locate pitches where I needed to. Just as in those middle innings, I made mistakes to really good hitters and they did what they should with it."
In all, Flaherty allowed five runs on eight hits over four innings with six strikeouts and one intentional walk.
"Good stuff and I told him that, and all he wanted to do was argue with me," manager Mke Matheny said. "I told him it wasn't time for that. Didn't say the execution was what he wanted but the stuff was right. The ball was coming out nice. Just didn't locate his fastball like I know that he can, like he knows that he can."
Flaherty's night began strong when he retired San Francisco's first three batters on 12 pitches while striking out leadoff man Denard Span and Joe Panik. Flaherty also had a 1-2-3 inning in the fourth before being removed for a pinch-hitter.
In between, though, Flaherty lost a little command and started leaving pitches over the middle of the plate.
After Buster Posey singled leading off the second, Crawford followed with a two-run home run to center. Two of the next three Giants batters singled before Span's two-out RBI single put the Giants up 3-0.
St. Louis cut the gap to 3-2 but Flaherty couldn't keep it close.
Posey reached on an infield single in the third and took third on Crawford's double. Hunter Pence then tripled in both runners to put the Giants up 5-2.
"I obviously expect more out of myself, especially with how I felt in the first inning," Flaherty said. "I wanted to carry that over and I don't think I did. I started rushing a little bit once I got in the stretch."
Matheny still came away satisfied with what he saw from Flaherty, even if the pitcher was critical of himself.
"You could see he expected a lot of himself and he felt like he made some mistakes in some situations where he didn't want to," Matheny said. "He may get away with those at other levels. He's got a real good idea of what he needs to do out there and I'm anxious to watch him do it again."
Rookie outfielder Harrison Bader also had a memorable night when he clubbed his first Major League home run in the third inning, a two-run blast that got the Cardinals on the scoreboard.
Afterwards an attendant in the St. Louis clubhouse tracked down the home run ball and was preparing to give it to Bader.
"When you get called up -- this is kind of my second time but it's still a small sample size -- you kind of want to get the first out of the way … your first hit, the first bag, whatever it is," Bader said. "Once you get all those little humps out of the way you can just really relax. Obviously, the home run came at a good time."