Black, a former pitcher, was dead on.
Wainwright tossed a four-hit shutout to lead the Cardinals to a 4-0 win before 39,151 at Busch Stadium.
San Diego, which lost for the second night in a row, falls to 4-12 on the road, the worst mark in the Majors.
Wainwright, who missed last season due to Tommy John surgery, fashioned his first complete game since August 6, 2010 against the Marlins. He struck out nine, walked one and was in total control from start to finish.
"That was the Adam Wainwright I remember before he got hurt," said San Diego catcher John Baker. "He's one of the top pitchers in baseball and I think he looked like that tonight for the first time this year."
Wainwright gave up doubles to Andy Parrino and pitching counterpart Edinson Volquez in the third and sixth innings. Yonder Alonso had a leadoff single in the seventh and pinch-hitter Blake Tekotte added one in the ninth.
The Padres had two runners on base only once -- in the ninth. Alonso drew a two-out walk but Jesus Guzman grounded out to end the game.
"That might be the best feeling I ever had pitching," Wainwright said. "I think it was a mindset of attacking hitters and making them hit my count."
Wainwright's stellar effort overshadowed a solid performance by Volquez, who gave up five hits and three earned runs over six innings.
Volquez surrendered two hits to the first four batters of the game before shutting St. Louis down over the next four innings. Volquez struck out just one batter, a season low.
Still, the right-hander was pleased with his performance.
"I think I did the best I could, I was battling the whole time," Volquez said. "I threw a lot of good pitches."
The Cardinals capitalized on a pair of defensive miscues to break open a one-run game with two runs in the sixth.
With runners on the corners, Beltran slapped a grounder to Alonso at first. Alonso had Daniel Descalso trapped between third and home and quickly rifled the ball to Parrino at third. Parrino fired home to Baker, and the throw got there in plenty of time, but Descalso managed to slide in under the tag.
"If that was anybody's fault it was mine for not being far enough in front of home plate to make the play," Baker said. "My mistakes of six or seven inches."
Later in the inning, shortstop Everth Cabrera booted a potential inning-ending double-play grounder off the bat of Greene with the bases loaded. Cabrera recovered to get the force at second, but Matt Holliday scored with the Cardinals' third run.
"That was one we should have turned," Black said.
The Padres, who entered the game with a .220 team batting average, have scored just 12 runs over the last six games. Wainwright added to those frustrations on Tuesday.
"He kept the ball on the corners, he broke some bats," Black said.
The streaking Alonso has hit safely in 21 of his last 24 games. He was doubled off first on a nice running catch by Holliday in the seventh.
Reliever Matt Palmer, who grew up 2 1/2 hours south of St. Louis in Caruthersville, Missouri, set the side down in order in the eighth.